Method and apparatus for performing synchronization in NR V2X

ABSTRACT

Provided are a method and an apparatus for performing, by a first device, wireless communication. The method may comprise the steps of: receiving, from a base station, first information related to SL synchronization priority; receiving, from the base station, second information indicating whether a base station-related synchronization reference can be selected as a synchronization source; and performing synchronization according to one synchronization reference of a GNSS-related synchronization reference and other terminals on the basis of the second information indicating that the base station-related synchronization reference cannot be selected as a synchronization source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 17/665,222, filed on Feb. 4, 2022, which is a continuation pursuant to 35 U.S.C. § 119(e) of international Application PCT/KR2020/011492, with an international filing data of Aug. 27, 2020, which claims the benefit of U.S. Provisional Patent Application No. 62/892,612, filed on Aug. 28, 2019 and U.S. Provisional Patent Application No. 62/893,810, filed on Aug. 30, 2019, the contents of which are hereby incorporated by reference herein in their entirety.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

This disclosure relates to a wireless communication system.

Related Art

Sidelink (SL) communication is a communication scheme in which a direct link is established between User Equipments (UEs) and the UEs exchange voice and data directly with each other without intervention of an evolved Node B (eNB). SL communication is under consideration as a solution to the overhead of an eNB caused by rapidly increasing data traffic.

Vehicle-to-everything (V2X) refers to a communication technology through which a vehicle exchanges information with another vehicle, a pedestrian, an object having an infrastructure (or infra) established therein, and so on. The V2X may be divided into 4 types, such as vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), and vehicle-to-pedestrian (V2P). The V2X communication may be provided via a PC5 interface and/or Uu interface.

Meanwhile, as a wider range of communication devices require larger communication capacities, the need for mobile broadband communication that is more enhanced than the existing Radio Access Technology (RAT) is rising. Accordingly, discussions are made on services and user equipment (UE) that are sensitive to reliability and latency. And, a next generation radio access technology that is based on the enhanced mobile broadband communication, massive Machine Type Communication (MTC), Ultra-Reliable and Low Latency Communication (URLLC), and so on, may be referred to as a new radio access technology (RAT) or new radio (NR). Herein, the NR may also support vehicle-to-everything (V2X) communication.

FIG. 1 is a drawing for describing V2X communication based on NR, compared to V2X communication based on RAT used before NR. The embodiment of FIG. 1 may be combined with various embodiments of the present disclosure.

Regarding V2X communication, a scheme of providing a safety service, based on a V2X message such as Basic Safety Message (BSM), Cooperative Awareness Message (CAM), and Decentralized Environmental Notification Message (DENM) is focused in the discussion on the RAT used before the NR. The V2X message may include position information, dynamic information, attribute information, or the like. For example, a UE may transmit a periodic message type CAM and/or an event triggered message type DENM to another UE.

For example, the CAM may include dynamic state information of the vehicle such as direction and speed, static data of the vehicle such as a size, and basic vehicle information such as an exterior illumination state, route details, or the like. For example, the UE may broadcast the CAM, and latency of the CAM may be less than 100 ms. For example, the UE may generate the DENM and transmit it to another UE in an unexpected situation such as a vehicle breakdown, accident, or the like. For example, all vehicles within a transmission range of the UE may receive the CAM and/or the DENM. In this case, the DENM may have a higher priority than the CAM.

Thereafter, regarding V2X communication, various V2X scenarios are proposed in NR. For example, the various V2X scenarios may include vehicle platooning, advanced driving, extended sensors, remote driving, or the like.

For example, based on the vehicle platooning, vehicles may move together by dynamically forming a group. For example, in order to perform platoon operations based on the vehicle platooning, the vehicles belonging to the group may receive periodic data from a leading vehicle. For example, the vehicles belonging to the group may decrease or increase an interval between the vehicles by using the periodic data.

For example, based on the advanced driving, the vehicle may be semi-automated or fully automated. For example, each vehicle may adjust trajectories or maneuvers, based on data obtained from a local sensor of a proximity vehicle and/or a proximity logical entity. In addition, for example, each vehicle may share driving intention with proximity vehicles.

For example, based on the extended sensors, raw data, processed data, or live video data obtained through the local sensors may be exchanged between a vehicle, a logical entity, a UE of pedestrians, and/or a V2X application server. Therefore, for example, the vehicle may recognize a more improved environment than an environment in which a self-sensor is used for detection.

For example, based on the remote driving, for a person who cannot drive or a remote vehicle in a dangerous environment, a remote driver or a V2X application may operate or control the remote vehicle. For example, if a route is predictable such as public transportation, cloud computing based driving may be used for the operation or control of the remote vehicle. In addition, for example, an access for a cloud-based back-end service platform may be considered for the remote driving.

Meanwhile, a scheme of specifying service requirements for various V2X scenarios such as vehicle platooning, advanced driving, extended sensors, remote driving, or the like is discussed in NR-based V2X communication.

SUMMARY OF THE DISCLOSURE

Technical Objects

Meanwhile, a UE needs to obtain synchronization from a synchronization reference in order to perform SL communication. For example, the synchronization reference may be at least one of a global navigation satellite systems (GNSS), a base station, a UE directly synchronized with the GNSS, a UE indirectly synchronized with the GNSS, a UE directly synchronized with the base station, a UE indirectly synchronized with the base station, and/or the remaining UEs. For example, in the synchronization procedure, the base station or the GNSS may be set to the highest priority. In this case, it is necessary to propose a method for the UE to select a synchronization reference and an apparatus supporting the same.

Technical Solutions

In one embodiment, a method for performing, by a first device, wireless communication is provided. The method may comprise: receiving, from a base station (BS), first information related to sidelink (SL) synchronization priority order, wherein the first information is set to Global Navigation Satellite Systems (GNSS)-based synchronization, wherein synchronization references related to the GNSS-based synchronization include a GNSS, GNSS-related synchronization references, BS-related synchronization references, and other user equipments (UEs), wherein the GNSS-related synchronization references include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS, wherein the BS-related synchronization references include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS, and wherein the GNSS has a higher synchronization priority than the UE directly synchronized with the GNSS, and the UE directly synchronized with the GNSS has a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS has a higher synchronization priority than the BS, and the BS has a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS has a higher synchronization priority than the UE indirectly synchronized with the BS, and the UE indirectly synchronized with the BS has a higher synchronization priority than the other UEs; receiving, from the BS, second information representing whether or not the BS-related synchronization references can be selected as a synchronization source; and performing synchronization with one synchronization reference among the GNSS-related synchronization references and the other UEs, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

EFFECTS OF THE DISCLOSURE

The user equipment (UE) may efficiently perform SL communication.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing for describing V2X communication based on NR, compared to V2X communication based on RAT used before NR.

FIG. 2 shows a structure of an NR system, based on an embodiment of the present disclosure.

FIG. 3 shows a functional division between an NG-RAN and a 5GC, based on an embodiment of the present disclosure.

FIG. 4 shows a radio protocol architecture, based on an embodiment of the present disclosure.

FIG. 5 shows a structure of an NR system, based on an embodiment of the present disclosure.

FIG. 6 shows a structure of a slot of an NR frame, based on an embodiment of the present disclosure.

FIG. 7 shows an example of a BWP, based on an embodiment of the present disclosure.

FIG. 8 shows a radio protocol architecture for a SL communication, based on an embodiment of the present disclosure.

FIG. 9 shows a UE performing V2X or SL communication, based on an embodiment of the present disclosure.

FIG. 10 shows a procedure of performing V2X or SL communication by a UE based on a transmission mode, based on an embodiment of the present disclosure.

FIG. 11 shows three cast types, based on an embodiment of the present disclosure.

FIG. 12 shows a synchronization source or synchronization reference of V2X, based on an embodiment of the present disclosure.

FIG. 13 shows a procedure for a UE to perform synchronization, based on an embodiment of the present disclosure.

FIG. 14 shows a method for a first device to perform synchronization, based on an embodiment of the present disclosure.

FIG. 15 shows a method for a second device to perform synchronization, based on an embodiment of the present disclosure.

FIG. 16 shows a method for a first device to perform wireless communication, based on an embodiment of the present disclosure.

FIG. 17 shows a method for a first device to perform wireless communication, based on an embodiment of the present disclosure.

FIG. 18 shows a communication system 1, based on an embodiment of the present disclosure.

FIG. 19 shows wireless devices, based on an embodiment of the present disclosure.

FIG. 20 shows a signal process circuit for a transmission signal, based on an embodiment of the present disclosure.

FIG. 21 shows another example of a wireless device, based on an embodiment of the present disclosure.

FIG. 22 shows a hand-held device, based on an embodiment of the present disclosure.

FIG. 23 shows a vehicle or an autonomous vehicle, based on an embodiment of the present disclosure.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the present disclosure, “A or B” may mean “only A”, “only B” or “both A and B.” In other words, in the present disclosure, “A or B” may be interpreted as “A and/or B”. For example, in the present disclosure, “A, B, or C” may mean “only A”, “only B”, “only C”, or “any combination of A, B, C”.

A slash (/) or comma used in the present disclosure may mean “and/or”. For example, “A/B” may mean “A and/or B”. Accordingly, “A/B” may mean “only A”, “only B”, or “both A and B”. For example, “A, B, C” may mean “A, B, or C”.

In the present disclosure, “at least one of A and B” may mean “only A”, “only B”, or “both A and B”. In addition, in the present disclosure, the expression “at least one of A or B” or “at least one of A and/or B” may be interpreted as “at least one of A and B”.

In addition, in the present disclosure, “at least one of A, B, and C” may mean “only A”, “only B”, “only C”, or “any combination of A, B, and C”. In addition, “at least one of A, B, or C” or “at least one of A, B, and/or C” may mean “at least one of A, B, and C”.

In addition, a parenthesis used in the present disclosure may mean “for example”. Specifically, when indicated as “control information (PDCCH)”, it may mean that “PDCCH” is proposed as an example of the “control information”. In other words, the “control information” of the present disclosure is not limited to “PDCCH”, and “PDCCH” may be proposed as an example of the “control information”. In addition, when indicated as “control information (i.e., PDCCH)”, it may also mean that “PDCCH” is proposed as an example of the “control information”.

A technical feature described individually in one figure in the present disclosure may be individually implemented, or may be simultaneously implemented.

The technology described below may be used in various wireless communication systems such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and so on. The CDMA may be implemented with a radio technology, such as universal terrestrial radio access (UTRA) or CDMA-2000. The TDMA may be implemented with a radio technology, such as global system for mobile communications (GSM)/general packet ratio service (GPRS)/enhanced data rate for GSM evolution (EDGE). The OFDMA may be implemented with a radio technology, such as institute of electrical and electronics engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, evolved UTRA (E-UTRA), and so on. IEEE 802.16m is an evolved version of IEEE 802.16e and provides backward compatibility with a system based on the IEEE 802.16e. The UTRA is part of a universal mobile telecommunication system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is part of an evolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses the OFDMA in a downlink and uses the SC-FDMA in an uplink. LTE-advanced (LTE-A) is an evolution of the LTE.

5G NR is a successive technology of LTE-A corresponding to a new Clean-slate type mobile communication system having the characteristics of high performance, low latency, high availability, and so on. 5G NR may use resources of all spectrum available for usage including low frequency bands of less than 1 GHz, middle frequency bands ranging from 1 GHz to 10 GHz, high frequency (millimeter waves) of 24 GHz or more, and so on.

For clarity in the description, the following description will mostly focus on LTE-A or 5G NR. However, technical features according to an embodiment of the present disclosure will not be limited only to this.

FIG. 2 shows a structure of an NR system, based on an embodiment of the present disclosure. The embodiment of FIG. 2 may be combined with various embodiments of the present disclosure.

Referring to FIG. 2 , a next generation-radio access network (NG-RAN) may include a BS 20 providing a UE 10 with a user plane and control plane protocol termination. For example, the BS 20 may include a next generation-Node B (gNB) and/or an evolved-NodeB (eNB). For example, the UE 10 may be fixed or mobile and may be referred to as other terms, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), wireless device, and so on. For example, the BS may be referred to as a fixed station which communicates with the UE 10 and may be referred to as other terms, such as a base transceiver system (BTS), an access point (AP), and so on.

The embodiment of FIG. 2 exemplifies a case where only the gNB is included. The BSs 20 may be connected to one another via Xn interface. The BS 20 may be connected to one another via 5th generation (5G) core network (5GC) and NG interface. More specifically, the BSs 20 may be connected to an access and mobility management function (AMF) 30 via NG-C interface, and may be connected to a user plane function (UPF) 30 via NG-U interface.

FIG. 3 shows a functional division between an NG-RAN and a 5GC, based on an embodiment of the present disclosure. The embodiment of FIG. 3 may be combined with various embodiments of the present disclosure.

Referring to FIG. 3 , the gNB may provide functions, such as Inter Cell Radio Resource Management (RRM), Radio Bearer (RB) control, Connection Mobility Control, Radio Admission Control, Measurement Configuration & Provision, Dynamic Resource Allocation, and so on. An AMF may provide functions, such as Non Access Stratum (NAS) security, idle state mobility processing, and so on. A UPF may provide functions, such as Mobility Anchoring, Protocol Data Unit (PDU) processing, and so on. A Session Management Function (SMF) may provide functions, such as user equipment (UE) Internet Protocol (IP) address allocation, PDU session control, and so on.

Layers of a radio interface protocol between the UE and the network can be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system. Among them, a physical (PHY) layer belonging to the first layer provides an information transfer service by using a physical channel, and a radio resource control (RRC) layer belonging to the third layer serves to control a radio resource between the UE and the network. For this, the RRC layer exchanges an RRC message between the UE and the BS.

FIG. 4 shows a radio protocol architecture, based on an embodiment of the present disclosure. The embodiment of FIG. 4 may be combined with various embodiments of the present disclosure. Specifically, FIG. 4(a) shows a radio protocol architecture for a user plane, and FIG. 4(b) shows a radio protocol architecture for a control plane. The user plane corresponds to a protocol stack for user data transmission, and the control plane corresponds to a protocol stack for control signal transmission.

Referring to FIG. 4 , a physical layer provides an upper layer with an information transfer service through a physical channel. The physical layer is connected to a medium access control (MAC) layer which is an upper layer of the physical layer through a transport channel. Data is transferred between the MAC layer and the physical layer through the transport channel. The transport channel is classified according to how and with what characteristics data is transmitted through a radio interface.

Between different physical layers, i.e., a physical layer of a transmitter and a physical layer of a receiver, data are transferred through the physical channel. The physical channel is modulated using an orthogonal frequency division multiplexing (OFDM) scheme, and utilizes time and frequency as a radio resource.

The MAC layer provides services to a radio link control (RLC) layer, which is a higher layer of the MAC layer, via a logical channel. The MAC layer provides a function of mapping multiple logical channels to multiple transport channels. The MAC layer also provides a function of logical channel multiplexing by mapping multiple logical channels to a single transport channel. The MAC layer provides data transfer services over logical channels.

The RLC layer performs concatenation, segmentation, and reassembly of Radio Link Control Service Data Unit (RLC SDU). In order to ensure diverse quality of service (QoS) required by a radio bearer (RB), the RLC layer provides three types of operation modes, i.e., a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (AM). An AM RLC provides error correction through an automatic repeat request (ARQ).

A radio resource control (RRC) layer is defined only in the control plane. The RRC layer serves to control the logical channel, the transport channel, and the physical channel in association with configuration, reconfiguration and release of RBs. The RB is a logical path provided by the first layer (i.e., the physical layer or the PHY layer) and the second layer (i.e., the MAC layer, the RLC layer, and the packet data convergence protocol (PDCP) layer) for data delivery between the UE and the network.

Functions of a packet data convergence protocol (PDCP) layer in the user plane include user data delivery, header compression, and ciphering. Functions of a PDCP layer in the control plane include control-plane data delivery and ciphering/integrity protection.

A service data adaptation protocol (SDAP) layer is defined only in a user plane. The SDAP layer performs mapping between a Quality of Service (QoS) flow and a data radio bearer (DRB) and QoS flow ID (QFI) marking in both DL and UL packets.

The configuration of the RB implies a process for specifying a radio protocol layer and channel properties to provide a particular service and for determining respective detailed parameters and operations. The RB can be classified into two types, i.e., a signaling RB (SRB) and a data RB (DRB). The SRB is used as a path for transmitting an RRC message in the control plane. The DRB is used as a path for transmitting user data in the user plane.

When an RRC connection is established between an RRC layer of the UE and an RRC layer of the E-UTRAN, the UE is in an RRC_CONNECTED state, and, otherwise, the UE may be in an RRC_IDLE state. In case of the NR, an RRC_INACTIVE state is additionally defined, and a UE being in the RRC_INACTIVE state may maintain its connection with a core network whereas its connection with the BS is released.

Data is transmitted from the network to the UE through a downlink transport channel. Examples of the downlink transport channel include a broadcast channel (BCH) for transmitting system information and a downlink-shared channel (SCH) for transmitting user traffic or control messages. Traffic of downlink multicast or broadcast services or the control messages can be transmitted on the downlink-SCH or an additional downlink multicast channel (MCH). Data is transmitted from the UE to the network through an uplink transport channel. Examples of the uplink transport channel include a random access channel (RACH) for transmitting an initial control message and an uplink SCH for transmitting user traffic or control messages.

Examples of logical channels belonging to a higher channel of the transport channel and mapped onto the transport channels include a broadcast channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), a multicast traffic channel (MTCH), etc.

The physical channel includes several OFDM symbols in a time domain and several sub-carriers in a frequency domain. One sub-frame includes a plurality of OFDM symbols in the time domain. A resource block is a unit of resource allocation, and consists of a plurality of OFDM symbols and a plurality of sub-carriers. Further, each subframe may use specific sub-carriers of specific OFDM symbols (e.g., a first OFDM symbol) of a corresponding subframe for a physical downlink control channel (PDCCH), i.e., an L1/L2 control channel. A transmission time interval (TTI) is a unit time of subframe transmission.

FIG. 5 shows a structure of an NR system, based on an embodiment of the present disclosure. The embodiment of FIG. 5 may be combined with various embodiments of the present disclosure.

Referring to FIG. 5 , in the NR, a radio frame may be used for performing uplink and downlink transmission. A radio frame has a length of 10 ms and may be defined to be configured of two half-frames (HFs). A half-frame may include five 1 ms subframes (SFs). A subframe (SF) may be divided into one or more slots, and the number of slots within a subframe may be determined based on subcarrier spacing (SCS). Each slot may include 12 or 14 OFDM(A) symbols according to a cyclic prefix (CP).

In case of using a normal CP, each slot may include 14 symbols. In case of using an extended CP, each slot may include 12 symbols. Herein, a symbol may include an OFDM symbol (or CP-OFDM symbol) and a Single Carrier-FDMA (SC-FDMA) symbol (or Discrete Fourier Transform-spread-OFDM (DFT-s-OFDM) symbol).

Table 1 shown below represents an example of a number of symbols per slot (N^(slot) _(symb)), a number slots per frame (N^(frame,u) _(slot)), and a number of slots per subframe (N^(subframe,u) _(slot)) based on an SCS configuration (u), in a case where a normal CP is used.

TABLE 1 SCS (15 * 2^(u)) N_(symb) ^(slot) N_(slot) ^(frame,u) N_(slot) ^(subframe,u)  15 KHz (u = 0) 14 10 1  30 KHz (u = 1) 14 20 2  60 KHz (u = 2) 14 40 4 120 KHz (u = 3) 14 80 8 240 KHz (u = 4) 14 160 16

Table 2 shows an example of a number of symbols per slot, a number of slots per frame, and a number of slots per subframe based on the SCS, in a case where an extended CP is used.

TABLE 2 SCS (15 * 2^(u)) N_(symb) ^(slot) N_(slot) ^(frame,u) N_(slot) ^(subframe,u) 60 KHz (u = 2) 12 40 4

In an NR system, OFDM(A) numerologies (e.g., SCS, CP length, and so on) between multiple cells being integrate to one UE may be differently configured. Accordingly, a (absolute time) duration (or section) of a time resource (e.g., subframe, slot or TTI) (collectively referred to as a time unit (TU) for simplicity) being configured of the same number of symbols may be differently configured in the integrated cells.

In the NR, multiple numerologies or SCSs for supporting diverse 5G services may be supported. For example, in case an SCS is 15 kHz, a wide area of the conventional cellular bands may be supported, and, in case an SCS is 30 kHz/60 kHz a dense-urban, lower latency, wider carrier bandwidth may be supported. In case the SCS is 60 kHz or higher, a bandwidth that is greater than 24.25 GHz may be used in order to overcome phase noise.

An NR frequency band may be defined as two different types of frequency ranges. The two different types of frequency ranges may be FR1 and FR2. The values of the frequency ranges may be changed (or varied), and, for example, the two different types of frequency ranges may be as shown below in Table 3. Among the frequency ranges that are used in an NR system, FR1 may mean a “sub 6 GHz range”, and FR2 may mean an “above 6 GHz range” and may also be referred to as a millimeter wave (mmW).

TABLE 3 Frequency Corresponding Subcarrier Range designation frequency range Spacing (SCS) FR1  450 MHz-6000 MHz 15, 30, 60 kHz FR2 24250 MHz-52600 MHz 60, 120, 240 kHz

As described above, the values of the frequency ranges in the NR system may be changed (or varied). For example, as shown below in Table 4, FR1 may include a band within a range of 410 MHz to 7125 MHz. More specifically, FR1 may include a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, and so on) and higher. For example, a frequency band of 6 GHz (or 5850, 5900, 5925 MHz, and so on) and higher being included in FR1 mat include an unlicensed band. The unlicensed band may be used for diverse purposes, e.g., the unlicensed band for vehicle-specific communication (e.g., automated driving).

TABLE 4 Frequency Corresponding Subcarrier Range designation frequency range Spacing (SCS) FR1  410 MHz-7125 MHz 15, 30, 60 kHz FR2 24250 MHz-52600 MHz 60, 120, 240 kHz

FIG. 6 shows a structure of a slot of an NR frame, based on an embodiment of the present disclosure. The embodiment of FIG. 6 may be combined with various embodiments of the present disclosure.

Referring to FIG. 6 , a slot includes a plurality of symbols in a time domain. For example, in case of a normal CP, one slot may include 14 symbols. However, in case of an extended CP, one slot may include 12 symbols. Alternatively, in case of a normal CP, one slot may include 7 symbols. However, in case of an extended CP, one slot may include 6 symbols.

A carrier includes a plurality of subcarriers in a frequency domain. A Resource Block (RB) may be defined as a plurality of consecutive subcarriers (e.g., 12 subcarriers) in the frequency domain. A Bandwidth Part (BWP) may be defined as a plurality of consecutive (Physical) Resource Blocks ((P)RBs) in the frequency domain, and the BWP may correspond to one numerology (e.g., SCS, CP length, and so on). A carrier may include a maximum of N number BWPs (e.g., 5 BWPs). Data communication may be performed via an activated BWP. Each element may be referred to as a Resource Element (RE) within a resource grid and one complex symbol may be mapped to each element.

Meanwhile, a radio interface between a UE and another UE or a radio interface between the UE and a network may consist of an L1 layer, an L2 layer, and an L3 layer. In various embodiments of the present disclosure, the L1 layer may imply a physical layer. In addition, for example, the L2 layer may imply at least one of a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer. In addition, for example, the L3 layer may imply an RRC layer.

Hereinafter, a bandwidth part (BWP) and a carrier will be described.

The BWP may be a set of consecutive physical resource blocks (PRBs) in a given numerology. The PRB may be selected from consecutive sub-sets of common resource blocks (CRBs) for the given numerology on a given carrier.

When using bandwidth adaptation (BA), a reception bandwidth and transmission bandwidth of a UE are not necessarily as large as a bandwidth of a cell, and the reception bandwidth and transmission bandwidth of the BS may be adjusted. For example, a network/BS may inform the UE of bandwidth adjustment. For example, the UE receive information/configuration for bandwidth adjustment from the network/BS. In this case, the UE may perform bandwidth adjustment based on the received information/configuration. For example, the bandwidth adjustment may include an increase/decrease of the bandwidth, a position change of the bandwidth, or a change in subcarrier spacing of the bandwidth.

For example, the bandwidth may be decreased during a period in which activity is low to save power. For example, the position of the bandwidth may move in a frequency domain. For example, the position of the bandwidth may move in the frequency domain to increase scheduling flexibility. For example, the subcarrier spacing of the bandwidth may be changed. For example, the subcarrier spacing of the bandwidth may be changed to allow a different service. A subset of a total cell bandwidth of a cell may be called a bandwidth part (BWP). The BA may be performed when the BS/network configures the BWP to the UE and the BS/network informs the UE of the BWP currently in an active state among the configured BWPs.

For example, the BWP may be at least any one of an active BWP, an initial BWP, and/or a default BWP. For example, the UE may not monitor downlink radio link quality in a DL BWP other than an active DL BWP on a primary cell (PCell). For example, the UE may not receive PDCCH, physical downlink shared channel (PDSCH), or channel state information-reference signal (CSI-RS) (excluding RRM) outside the active DL BWP. For example, the UE may not trigger a channel state information (CSI) report for the inactive DL BWP. For example, the UE may not transmit physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH) outside an active UL BWP. For example, in a downlink case, the initial BWP may be given as a consecutive RB set for a remaining minimum system information (RMSI) control resource set (CORESET) (configured by physical broadcast channel (PBCH)). For example, in an uplink case, the initial BWP may be given by system information block (SIB) for a random access procedure. For example, the default BWP may be configured by a higher layer. For example, an initial value of the default BWP may be an initial DL BWP. For energy saving, if the UE fails to detect downlink control information (DCI) during a specific period, the UE may switch the active BWP of the UE to the default BWP.

Meanwhile, the BWP may be defined for SL. The same SL BWP may be used in transmission and reception. For example, a transmitting UE may transmit a SL channel or a SL signal on a specific BWP, and a receiving UE may receive the SL channel or the SL signal on the specific BWP. In a licensed carrier, the SL BWP may be defined separately from a Uu BWP, and the SL BWP may have configuration signaling separate from the Uu BWP. For example, the UE may receive a configuration for the SL BWP from the BS/network. The SL BWP may be (pre-)configured in a carrier with respect to an out-of-coverage NR V2X UE and an RRC_IDLE UE. For the UE in the RRC_CONNECTED mode, at least one SL BWP may be activated in the carrier.

FIG. 7 shows an example of a BWP, based on an embodiment of the present disclosure. The embodiment of FIG. 7 may be combined with various embodiments of the present disclosure. It is assumed in the embodiment of FIG. 7 that the number of BWPs is 3.

Referring to FIG. 7 , a common resource block (CRB) may be a carrier resource block numbered from one end of a carrier band to the other end thereof. In addition, the PRB may be a resource block numbered within each BWP. A point A may indicate a common reference point for a resource block grid.

The BWP may be configured by a point A, an offset N^(start) _(BWP) from the point A, and a bandwidth N^(size) _(BWP). For example, the point A may be an external reference point of a PRB of a carrier in which a subcarrier 0 of all numerologies (e.g., all numerologies supported by a network on that carrier) is aligned. For example, the offset may be a PRB interval between a lowest subcarrier and the point A in a given numerology. For example, the bandwidth may be the number of PRBs in the given numerology.

Hereinafter, V2X or SL communication will be described.

FIG. 8 shows a radio protocol architecture for a SL communication, based on an embodiment of the present disclosure. The embodiment of FIG. 8 may be combined with various embodiments of the present disclosure. More specifically, FIG. 8(a) shows a user plane protocol stack, and FIG. 8(b) shows a control plane protocol stack.

Hereinafter, a sidelink synchronization signal (SLSS) and synchronization information will be described.

The SLSS may include a primary sidelink synchronization signal (PSSS) and a secondary sidelink synchronization signal (SSSS), as a SL-specific sequence. The PSSS may be referred to as a sidelink primary synchronization signal (S-PSS), and the SSSS may be referred to as a sidelink secondary synchronization signal (S-SSS). For example, length-127 M-sequences may be used for the S-PSS, and length-127 gold sequences may be used for the S-SSS. For example, a UE may use the S-PSS for initial signal detection and for synchronization acquisition. For example, the UE may use the S-PSS and the S-SSS for acquisition of detailed synchronization and for detection of a synchronization signal ID.

A physical sidelink broadcast channel (PSBCH) may be a (broadcast) channel for transmitting default (system) information which must be first known by the UE before SL signal transmission/reception. For example, the default information may be information related to SLSS, a duplex mode (DM), a time division duplex (TDD) uplink/downlink (UL/DL) configuration, information related to a resource pool, a type of an application related to the SLSS, a subframe offset, broadcast information, or the like. For example, for evaluation of PSBCH performance, in NR V2X, a payload size of the PSBCH may be 56 bits including 24-bit cyclic redundancy check (CRC).

The S-PSS, the S-SSS, and the PSBCH may be included in a block format (e.g., SL synchronization signal (SS)/PSBCH block, hereinafter, sidelink-synchronization signal block (S-SSB)) supporting periodical transmission. The S-SSB may have the same numerology (i.e., SCS and CP length) as a physical sidelink control channel (PSCCH)/physical sidelink shared channel (PSSCH) in a carrier, and a transmission bandwidth may exist within a (pre-)configured sidelink (SL) BWP. For example, the S-SSB may have a bandwidth of 11 resource blocks (RBs). For example, the PSBCH may exist across 11 RBs. In addition, a frequency position of the S-SSB may be (pre-)configured. Accordingly, the UE does not have to perform hypothesis detection at frequency to discover the S-SSB in the carrier.

FIG. 9 shows a UE performing V2X or SL communication, based on an embodiment of the present disclosure. The embodiment of FIG. 9 may be combined with various embodiments of the present disclosure.

Referring to FIG. 9 , in V2X or SL communication, the term ‘UE’ may generally imply a UE of a user. However, if a network equipment such as a BS transmits/receives a signal according to a communication scheme between UEs, the BS may also be regarded as a sort of the UE. For example, a UE 1 may be a first apparatus 100, and a UE 2 may be a second apparatus 200.

For example, the UE 1 may select a resource unit corresponding to a specific resource in a resource pool which implies a set of series of resources. In addition, the UE 1 may transmit a SL signal by using the resource unit. For example, a resource pool in which the UE 1 is capable of transmitting a signal may be configured to the UE 2 which is a receiving UE, and the signal of the UE 1 may be detected in the resource pool.

Herein, if the UE 1 is within a connectivity range of the BS, the BS may inform the UE 1 of the resource pool. Otherwise, if the UE 1 is out of the connectivity range of the BS, another UE may inform the UE 1 of the resource pool, or the UE 1 may use a pre-configured resource pool.

In general, the resource pool may be configured in unit of a plurality of resources, and each UE may select a unit of one or a plurality of resources to use it in SL signal transmission thereof.

Hereinafter, resource allocation in SL will be described.

FIG. 10 shows a procedure of performing V2X or SL communication by a UE based on a transmission mode, based on an embodiment of the present disclosure. The embodiment of FIG. 10 may be combined with various embodiments of the present disclosure. In various embodiments of the present disclosure, the transmission mode may be called a mode or a resource allocation mode. Hereinafter, for convenience of explanation, in LTE, the transmission mode may be called an LTE transmission mode. In NR, the transmission mode may be called an NR resource allocation mode.

For example, FIG. 10(a) shows a UE operation related to an LTE transmission mode 1 or an LTE transmission mode 3. Alternatively, for example, FIG. 10(a) shows a UE operation related to an NR resource allocation mode 1. For example, the LTE transmission mode 1 may be applied to general SL communication, and the LTE transmission mode 3 may be applied to V2X communication.

For example, FIG. 10(b) shows a UE operation related to an LTE transmission mode 2 or an LTE transmission mode 4. Alternatively, for example, FIG. 10(b) shows a UE operation related to an NR resource allocation mode 2.

Referring to FIG. 10(a), in the LTE transmission mode 1, the LTE transmission mode 3, or the NR resource allocation mode 1, a BS may schedule a SL resource to be used by the UE for SL transmission. For example, the BS may perform resource scheduling to a UE 1 through a PDCCH (more specifically, downlink control information (DCI)), and the UE 1 may perform V2X or SL communication with respect to a UE 2 according to the resource scheduling. For example, the UE 1 may transmit a sidelink control information (SCI) to the UE 2 through a physical sidelink control channel (PSCCH), and thereafter transmit data based on the SCI to the UE 2 through a physical sidelink shared channel (PSSCH).

Referring to FIG. 10(b), in the LTE transmission mode 2, the LTE transmission mode 4, or the NR resource allocation mode 2, the UE may determine a SL transmission resource within a SL resource configured by a BS/network or a pre-configured SL resource. For example, the configured SL resource or the pre-configured SL resource may be a resource pool. For example, the UE may autonomously select or schedule a resource for SL transmission. For example, the UE may perform SL communication by autonomously selecting a resource within a configured resource pool. For example, the UE may autonomously select a resource within a selective window by performing a sensing and resource (re)selection procedure. For example, the sensing may be performed in unit of subchannels. In addition, the UE 1 which has autonomously selected the resource within the resource pool may transmit the SCI to the UE 2 through a PSCCH, and thereafter may transmit data based on the SCI to the UE 2 through a PSSCH.

FIG. 11 shows three cast types, based on an embodiment of the present disclosure. The embodiment of FIG. 11 may be combined with various embodiments of the present disclosure. Specifically, FIG. 11(a) shows broadcast-type SL communication, FIG. 11(b) shows unicast type-SL communication, and FIG. 11(c) shows groupcast-type SL communication. In case of the unicast-type SL communication, a UE may perform one-to-one communication with respect to another UE. In case of the groupcast-type SL transmission, the UE may perform SL communication with respect to one or more UEs in a group to which the UE belongs. In various embodiments of the present disclosure, SL groupcast communication may be replaced with SL multicast communication, SL one-to-many communication, or the like.

FIG. 12 shows a synchronization source or synchronization reference of V2X, based on an embodiment of the present disclosure. The embodiment of FIG. 12 may be combined with various embodiments of the present disclosure.

Referring to FIG. 12 , in V2X, a UE may be directly synchronized with a global navigation satellite system (GNSS), or may be indirectly synchronized with the GNSS through a UE (inside network coverage or outside network coverage) directly synchronized with the GNSS. If the GNSS is configured as the synchronization source, the UE may calculate a DFN and a subframe number by using a coordinated universal time (UTC) and a (pre-)configured direct frame number (DFN) offset.

Alternatively, the UE may be directly synchronized with a BS, or may be synchronized with another UE which is time/frequency-synchronized with the BS. For example, the BS may be an eNB or a gNB. For example, if the UE is inside the network coverage, the UE may receive synchronization information provided by the BS, and may be directly synchronized with the BS. Thereafter, the UE may provide the synchronization information to adjacent another UE. If BS timing is configured based on synchronization, for synchronization and downlink measurement, the UE may be dependent on a cell related to a corresponding frequency (when it is inside the cell coverage at the frequency), or a primary cell or a serving cell (when it is outside the cell coverage at the frequency).

The BS (e.g., serving cell) may provide a synchronization configuration for a carrier used in V2X or SL communication. In this case, the UE may conform to the synchronization configuration received from the BS. If the UE fails to detect any cell in a carrier used in the V2X or SL communication and fails to receive the synchronization configuration from the serving cell, the UE may conform to a pre-configured synchronization configuration.

Alternatively, the UE may be synchronized with another UE which fails to obtain synchronization information directly or indirectly from the BS or the GNSS. A synchronization source or preference may be pre-configured to the UE. Alternatively, the synchronization source and preference may be configured through a control message provided by the BS.

A SL synchronization source may be associated/related with a synchronization priority. For example, a relation between the synchronization source and the synchronization priority may be defined as shown in Table 5 or Table 6. Table 5 or Table 6 are for exemplary purposes only, and the relation between the synchronization source and the synchronization priority may be defined in various forms.

TABLE 5 Priority GNSS-based eNB/gNB-based level synchronization synchronization P0 GNSS BS P1 All UEs directly All UEs directly synchronized with GNSS synchronized with BS P2 All UEs indirectly synchronized All UEs indirectly synchronized with GNSS with BS P3 All other UEs GNSS P4 N/A All UEs directly synchronized with GNSS P5 N/A All UEs indirectly synchronized with GNSS P6 N/A All other UEs

TABLE 6 Priority GNSS-based eNB/gNB-based level synchronization synchronization P0 GNSS BS P1 All UEs directly All UEs directly synchronized synchronized with GNSS with BS P2 All UEs indirectly All UEs indirectly synchronized synchronized with GNSS with BS P3 BS GNSS P4 All UEs directly All UEs directly synchronized synchronized with BS with GNSS P5 All UEs indirectly All UEs indirectly synchronized synchronized with BS with GNSS P6 Remaining UE(s) having Remaining UE(s) having low priority low priority

In Table 5 or Table 6, P0 may denote a highest priority, and P6 may denote a lowest priority. In Table 5 or Table 6, the BS may include at least one of a gNB and an eNB.

Whether to use GNSS-based synchronization or BS-based synchronization may be (pre-)configured. In a single-carrier operation, the UE may derive transmission timing of the UE from an available synchronization reference having the highest priority.

Hereinafter, carrier reselection will be described.

In V2X or SL communication, a UE may perform carrier reselection based on a channel busy ratio (CBR) of configured carriers and/or a ProSe per-packet priority (PPPP) of a V2X message to be transmitted. For example, the carrier reselection may be performed by a MAC layer of the UE.

CBR may mean the portion of sub-channels in a resource pool in which a sidelink-received signal strength indicator (S-RSSI) measured by the UE is detected to be greater than a pre-configured threshold. There may be a PPPP related to each logical channel, and a configuration of the PPPP value shall reflect a latency required in both a UE and a BS. In carrier reselection, the UE may select one or more carriers from among candidate carriers starting from a lowest CBR in an ascending order of the CBR.

Meanwhile, in the present disclosure, for example, a transmitting UE (TX UE) may be a UE which transmits data to a (target) receiving UE (RX UE). For example, the TX UE may be a UE which performs PSCCH transmission and/or PSSCH transmission. Additionally/alternatively, the TX UE may be a UE which transmits SL CSI-RS(s) and/or a SL CSI report request indicator to the (target) RX UE. Additionally/alternatively, the TX UE may be a UE which transmits a (control) channel (e.g., PSCCH, PSSCH, etc.) and/or reference signal(s) on the (control) channel (e.g., DM-RS, CSI-RS, etc.), to be used for a SL RLM operation and/or a SL RLF operation of the (target) RX UE.

Meanwhile, in the present disclosure, for example, a receiving UE (RX UE) may be a UE which transmits SL HARQ feedback to a transmitting UE (TX UE) based on whether decoding of data received from the TX UE is successful and/or whether detection/decoding of a PSCCH (related to PSSCH scheduling) transmitted by the TX UE is successful. Additionally/alternatively, the RX UE may be a UE which performs SL CSI transmission to the TX UE based on SL CSI-RS(s) and/or a SL CSI report request indicator received from the TX UE. Additionally/alternatively, the RX UE is a UE which transmits a SL (L1) RSRP measurement value, to the TX UE, measured based on (pre-defined) reference signal(s) and/or a SL (L1) RSRP report request indicator received from the TX UE. Additionally/alternatively, the RX UE may be a UE which transmits data of the RX UE to the TX UE. Additionally/alternatively, the RX UE may be a UE which performs a SL RLM operation and/or a SL RLF operation based on a (pre-configured) (control) channel and/or reference signal(s) on the (control) channel received from the TX UE.

Meanwhile, in the present disclosure, for example, in case the RX UE transmits SL HARQ feedback information for a PSSCH and/or a PSCCH received from the TX UE, the following options or some of the following options may be considered. Herein, for example, the following options or some of the following options may be limitedly applied only if the RX UE successfully decodes/detects a PSCCH scheduling a PSSCH.

Option 1) NACK information may be transmitted to the TX UE only if the RX UE fails to decode/receive the PSSCH received from the TX UE.

Option 2) If the RX UE succeeds in decoding/receiving the PSSCH received from the TX UE, ACK information may be transmitted to the TX UE, and if the RX UE fails to decode/receive the PSSCH, NACK information may be transmitted to the TX UE.

Meanwhile, in the present disclosure, for example, the TX UE may transmit the following information or some of the following information to the RX UE through SCI(s). Herein, for example, the TX UE may transmit some or all of the following information to the RX UE through a first SCI and/or a second SCI.

-   -   PSSCH (and/or PSCCH) related resource allocation information         (e.g., the location/number of time/frequency resources, resource         reservation information (e.g., period))     -   SL CSI report request indicator or SL (L1) RSRP (and/or SL (L1)         RSRQ and/or SL (L1) RSSI) report request indicator     -   SL CSI transmission indicator (or SL (L1) RSRP (and/or SL (L1)         RSRQ and/or SL (L1) RSSI) information transmission indicator)         (on a PSSCH)     -   Modulation and Coding Scheme (MCS) information     -   TX power information     -   L1 destination ID information and/or L1 source ID information     -   SL HARQ process ID information     -   NDI information     -   RV information     -   (Transmission traffic/packet related) QoS information (e.g.,         priority information)     -   SL CSI-RS transmission indicator or information on the number of         antenna ports for (transmitting) SL CSI-RS     -   TX UE location information or location (or distance range)         information of the target RX UE (for which SL HARQ feedback is         requested)     -   Reference signal (e.g., DM-RS, etc.) information related to         decoding (and/or channel estimation) of data transmitted through         a PSSCH. For example, information related to a pattern of         (time-frequency) mapping resources of DM-RS(s), RANK         information, antenna port index information, etc.

Meanwhile, in the present disclosure, for example, since the TX UE may transmit a SCI, a first SCI and/or a second SCI to the RX UE through a PSCCH, the PSCCH may be replaced/substituted with the SCI and/or the first SCI and/or the second SCI. Additionally/alternatively, the SCI may be replaced/substituted with the PSCCH and/or the first SCI and/or the second SCI. Additionally/alternatively, for example, since the TX UE may transmit a second SCI to the RX UE through a PSSCH, the PSSCH may be replaced/substituted with the second SCI.

Meanwhile, in the present disclosure, for example, if SCI configuration fields are divided into two groups in consideration of a (relatively) high SCI payload size, the first SCI including a first SCI configuration field group may be referred to as a first SCI, and the second SCI including a second SCI configuration field group may be referred to as a second SCI. Also, for example, the first SCI may be transmitted to the receiving UE through a PSCCH. Also, for example, the second SCI may be transmitted to the receiving UE through a (independent) PSCCH or may be piggybacked and transmitted together with data through a PSSCH.

Meanwhile, in the present disclosure, for example, “configuration” or “definition” may mean a (pre)configuration from a base station or a network (through predefined signaling (e.g., SIB, MAC, RRC, etc.)) (for each resource pool).

Meanwhile, in the present disclosure, for example, since an RLF may be determined based on out-of-synch (OOS) indicator(s) or in-synch (IS) indicator(s), the RLF may be replaced/substituted with out-of-synch (OOS) indicator(s) or in-synch (IS) indicator(s).

Meanwhile, in the present disclosure, for example, an RB may be replaced/substituted with a subcarrier. Also, in the present disclosure, for example, a packet or a traffic may be replaced/substituted with a TB or a MAC PDU based on a transmission layer.

Meanwhile, in the present disclosure, a CBG or a CG may be replaced/substituted with a TB.

Meanwhile, in the present disclosure, for example, a source ID may be replaced/substituted with a destination ID.

Meanwhile, in the present disclosure, for example, an L1 ID may be replaced/substituted with an L2 ID. For example, the L1 ID may be an L1 source ID or an L1 destination ID. For example, the L2 ID may be an L2 source ID or an L2 destination ID.

Meanwhile, in the present disclosure, for example, an operation of the transmitting UE to reserve/select/determine retransmission resource(s) may include: an operation of the transmitting UE to reserve/select/determine potential retransmission resource(s) for which actual use will be determined based on SL HARQ feedback information received from the receiving UE.

Meanwhile, in the present disclosure, SL mode 1 may refer to a resource allocation method or a communication method in which a base station directly schedules sidelink transmission (SL TX) resource(s) of a UE through predefined signaling (e.g., DCI). Also, for example, SL mode 2 may refer to a resource allocation method or a communication method in which a UE independently selects SL TX resource(s) within a resource pool configured or pre-configured from a base station or a network.

Meanwhile, in the present disclosure, for example, for convenience of description, a (physical) channel used when the RX UE transmits at least one of the following information to the TX UE may be referred to as a PSFCH.

-   -   SL HARQ feedback, SL CSI, SL (L1) RSRP

Meanwhile, in the present disclosure, a base station may include at least one of a gNB and an eNB.

Based on an embodiment of the present disclosure, in the case of SL communication, information regarding which entity-related time synchronization and/or frequency synchronization has a (relatively) high priority among the base station or the GNSS may be configured or pre-configured for the UE by the network/base station. For example, the network/base station may transmit information regarding which entity has a high synchronization priority among the base station and the GNSS to the UE. For example, the information may be sl-SyncPriority.

For example, the base station may transmit a SL-FreqConfigCommon information element (IE) to the UE. For example, Table 7 shows the SL-FreqConfigCommon IE.

TABLE 7 -- ASN1START -- TAG-SL-FREQCONFIGCOMMON-START  SL-FreqConfigCommon-r16 ::=  SEQUENCE {   sl-SCS-SpecificCarrierList-r16 SEQUENCE (SIZE (1 . . .   maxSCSs)) OF SCS-SpecificCarrier,   sl-AbsoluteFrequencyPointA-r16  ARFCN-ValueNR,   sl-AbsoluteFrequencySSB-r16 ARFCN-ValueNR   OPTIONAL, -- Need R   frequencyShift7p5khzSL-r16 ENUMERATED  {true}  OPTIONAL, -- Cond V2X-SL-Shared   valueN-r16 INTEGER (−1 . . . 1),   sl-BWP-List-r16 SEQUENCE (SIZE (1 . . . maxNrofSL-  BWPs-r16)) OF SL-BWP-ConfigCommon-r16 OPTIONAL,   -- Need R   sl-SyncPriority-r16 ENUMERATED {gnss, gnbEnb}   OPTIONAL, -- Need R   sl-NbAsSync-r16 BOOLEAN OPTIONAL, -- Need R   sl-SyncConfigList-r16 SL-SyncConfigList-r16 OPTIONAL,   -- Need R   . . .  } -- TAG-SL-FREQCONFIGCOMMON-STOP -- ASN1STOP

Referring to Table 7, the SL-FreqConfigCommon IE may include sl-SyncPriority and/or sl-NbAsSync. For example, sl-SyncPriority may indicate/represent synchronization priority order. For example, sl-NbAsSync may indicate/represent whether the base station/network can be selected as a synchronization reference. For example, if the UE receives sl-SyncPriority indicating/representing gnss from the base station, the UE may determine that the GNSS has the highest synchronization priority, and the UE may select a synchronization reference based on priorities related to the GNSS-based synchronization (i.e., the left column) of Table 5, Table 6 or Table 8. For example, if the UE receives sl-SyncPriority indicating/representing gnbEnb from the base station, the UE may determine that the base station has the highest synchronization priority, and the UE may select a synchronization reference based on priorities related to the BS-based synchronization (eNB/gNB-based synchronization) (i.e., the right column) of Table 5, Table 6 or Table 8. For example, if the UE does not receive sl-SyncPriority from the base station, the UE may determine that the GNSS has the highest synchronization priority, and the UE may select a synchronization reference based on priorities related to the GNSS-based synchronization (i.e., the left column) of Table 5, Table 6 or Table 8.

For example, if the base station is set to a (relatively) higher priority than the GNSS (e.g., if sl-SyncPriority indicates/represents gnbEnb), the UE may consider/determine the priority of the synchronization source/reference based on the right column of Table 5, Table 6, or Table 8 (i.e., the priority related to BS-based synchronization). On the other hand, for example, if the GNSS is set to a (relatively) higher priority than the base station (e.g., if sl-SyncPriority indicates/represents gnss or sl-SyncPriority is not configured), the UE may consider/determine the priority of the synchronization source/reference based on the left column of Table 5, Table 6, or Table 8 (i.e., the priority related to GNSS-based synchronization).

TABLE 8 BS-based synchronization GNSS-based synchronization (eNB/gNB-based synchronization) PRIORITY 0: GNSS PRIORITY 0: BS PRIORITY 1: UE directly PRIORITY 1: UE directly synchronized with GNSS synchronized with BS PRIORITY 2: UE indirectly PRIORITY 2: UE indirectly synchronized with GNSS synchronized with BS PRIORITY 3: BS PRIORITY 3: GNSS PRIORITY 4: UE directly PRIORITY 4: UE directly synchronized with BS synchronized with GNSS PRIORITY 5: UE indirectly PRIORITY 5: UE indirectly synchronized with BS synchronized with GNSS PRIORITY 6: remaining UE(s) PRIORITY 6: remaining UE(s) having lowest priority having lowest priority

Herein, for example, in the term “PRIORITY X” of Table 8, a (relatively) smaller X value may refer to a higher priority. For example, the PRIORITY 0 may be a higher priority than the PRIORITY 1, and the PRIORITY 1 may be a higher priority than the PRIORITY 2.

Based on an embodiment of the present disclosure, information related to whether or not a base station (potentially) exists may be signaled/transmitted by the network or the base station to the UE. For example, information related to whether or not a base station (potentially) exists may be signaled/transmitted by the network or the base station to the UE for each carrier. For example, information related to whether or not a base station (potentially) exists may be signaled/transmitted by the network or the base station to the UE for each resource pool. For example, information related to whether or not a base station (potentially) exists may be signaled/transmitted by the network or the base station to the UE for each SL BWP. For example, information related to whether or not a base station is (potentially) considered as a synchronization source/reference may be signaled/transmitted by the network or the base station to the UE. For example, information related to whether or not a base station is (potentially) considered as a synchronization source/reference may be signaled/transmitted by the network or the base station to the UE for each carrier. For example, information related to whether or not a base station is (potentially) considered as a synchronization source/reference may be signaled/transmitted by the network or the base station to the UE for each resource pool. For example, information related to whether or not a base station is (potentially) considered as a synchronization source/reference may be signaled/transmitted by the network or the base station to the UE for each SL BWP. Hereinafter, it will be described in detail with reference to the drawings.

FIG. 13 shows a procedure for a UE to perform synchronization, based on an embodiment of the present disclosure. The embodiment of FIG. 13 may be combined with various embodiments of the present disclosure.

Referring to FIG. 13 , in step S1310, the base station/network may transmit sl-NbAsSync to the UE. For example, sl-NbAsSync may be information related to whether a base station/network exists (potentially) or not. For example, sl-NbAsSync may indicate/represent whether a base station/network exists (potentially) or not. For example, sl-NbAsSync may be information related to whether a base station/network is (potentially) considered as a synchronization source/reference or not. For example, sl-NbAsSync may indicate/represent whether a base station/network is (potentially) considered as a synchronization source/reference or not. For example, sl-NbAsSync may be information related to whether a base station/network can be selected as a synchronization reference. For example, sl-NbAsSync may indicate/represent whether a base station/network can be selected as a synchronization reference. For example, sl-NbAsSync may be configured for the UE for each carrier. For example, sl-NbAsSync may be configured for the UE for each resource pool. For example, sl-NbAsSync may be configured for the UE for each SL BWP.

In step S1320, the UE may select a synchronization reference based on sl-SyncPriority and/or sl-NbAsSync. For example, the synchronization reference may be at least one of a GNSS, a UE directly synchronized with the GNSS, a UE indirectly synchronized with the GNSS, a base station, a UE directly synchronized with the base station, a UE indirectly synchronized with the base station, and/or the remaining UE(s) having the lowest priority.

For example, if the UE receives sl-SyncPriority indicating/representing gnss from the base station, the UE may select a synchronization reference based on priorities related to the GNSS-based synchronization (i.e., the left column) of Table 5, Table 6 or Table 8. For example, if the UE receives sl-SyncPriority indicating/representing gnbEnb from the base station, the UE may select a synchronization reference based on priorities related to the BS-based synchronization (eNB/gNB-based synchronization) (i.e., the right column) of Table 5, Table 6 or Table 8. For example, if the UE does not receive sl-SyncPriority from the base station, the UE may select a synchronization reference based on priorities related to the GNSS-based synchronization (i.e., the left column) of Table 5, Table 6 or Table 8.

For example, if the UE selects a synchronization reference based on priorities related to the GNSS-based synchronization (i.e., the left column) of Table 5, Table 6 or Table 8, and if sl-NbAsSync indicates/represent that a base station/network cannot be selected as the synchronization reference, the UE cannot select i) a base station, ii) a UE directly synchronized with the base station, and iii) a UE indirectly synchronized with the base station as the synchronization reference. In this case, the UE may select at least one of a GNSS, a UE directly synchronized with the GNSS, a UE indirectly synchronized with the GNSS, and/or the remaining UE(s) having the lowest priority as the synchronization reference.

For example, if the UE selects a synchronization reference based on priorities related to the GNSS-based synchronization (i.e., the left column) of Table 5, Table 6 or Table 8, and if sl-NbAsSync indicates/represent that a base station/network can be selected as the synchronization reference, the UE can select i) a base station, ii) a UE directly synchronized with the base station, and iii) a UE indirectly synchronized with the base station as the synchronization reference. In this case, the UE may select at least one of a GNSS, a UE directly synchronized with the GNSS, a UE indirectly synchronized with the GNSS, a base station, a UE directly synchronized with the base station, a UE indirectly synchronized with the base station, and/or the remaining UE(s) having the lowest priority as the synchronization reference.

For example, the UE may be configured not to search for/detect BS-related synchronization signal(s), on a carrier signaled/indicated that a base station does not exist (potentially). In the present disclosure, for convenience of description, the BS-related synchronization signal(s) (e.g., synchronization-related signal(s) transmitted by a base station) may be referred to as GE_SYCH. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a carrier signaled/indicated that a base station does not exist (potentially). Additionally, for example, the UE may be configured not to search for/detect SL synchronization signal(s) referring to time synchronization and/or frequency synchronization of a base station or SL synchronization signal(s) derived from a time and/or a frequency of a base station, on a carrier signaled/indicated that a base station does not exist (potentially). In the present disclosure, for convenience of description, the SL synchronization signal(s) referring to the time synchronization and/or the frequency synchronization of the base station or the SL synchronization signal(s) derived from the time and/or the frequency of the base station may be referred to as SL_SYCH. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a carrier signaled/indicated that a base station does not exist (potentially). For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a base station does not exist (potentially). On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a carrier signaled/indicated that a base station exists (potentially). In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a base station exists (potentially).

For example, the UE may be configured not to search for/detect GE_SYCH, on a resource pool signaled/indicated that a base station does not exist (potentially). For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a resource pool signaled/indicated that a base station does not exist (potentially). Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a resource pool signaled/indicated that a base station does not exist (potentially). For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a resource pool signaled/indicated that a base station does not exist (potentially). For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a resource pool signaled/indicated that a base station does not exist (potentially). On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a resource pool signaled/indicated that a base station exists (potentially). In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a resource pool signaled/indicated that a base station exists (potentially).

For example, the UE may be configured not to search for/detect GE_SYCH, on a SL BWP signaled/indicated that a base station does not exist (potentially). For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a SL BWP signaled/indicated that a base station does not exist (potentially). Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a SL BWP signaled/indicated that a base station does not exist (potentially). For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a SL BWP signaled/indicated that a base station does not exist (potentially). For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a SL BWP signaled/indicated that a base station does not exist (potentially). On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a SL BWP signaled/indicated that a base station exists (potentially). In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a SL BWP signaled/indicated that a base station exists (potentially).

For example, the UE may be configured not to search for/detect GE_SYCH, on a carrier signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a carrier signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a carrier signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a carrier signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a carrier signaled/indicated that a base station/network needs to be considered (potentially) as a synchronization source/reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a base station/network needs to be considered (potentially) as a synchronization source/reference.

For example, the UE may be configured not to search for/detect GE_SYCH, on a resource pool signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a resource pool signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network needs to be considered (potentially) as a synchronization source/reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network needs to be considered (potentially) as a synchronization source/reference.

For example, the UE may be configured not to search for/detect GE_SYCH, on a SL BWP signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a SL BWP signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network need not be considered (potentially) as a synchronization source/reference. On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network needs to be considered (potentially) as a synchronization source/reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network needs to be considered (potentially) as a synchronization source/reference.

For example, the UE may be configured not to search for/detect GE_SYCH, on a carrier signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a carrier signaled/indicated that a base station/network cannot be selected as a synchronization reference. Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a carrier signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a carrier signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a base station/network cannot be selected as a synchronization reference. On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a carrier signaled/indicated that a base station/network can be selected as a synchronization reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a base station/network can be selected as a synchronization reference.

For example, the UE may be configured not to search for/detect GE_SYCH, on a resource pool signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network cannot be selected as a synchronization reference. Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a resource pool signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network cannot be selected as a synchronization reference. On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network can be selected as a synchronization reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a resource pool signaled/indicated that a base station/network can be selected as a synchronization reference.

For example, the UE may be configured not to search for/detect GE_SYCH, on a SL BWP signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network cannot be selected as a synchronization reference. Additionally, for example, the UE may be configured not to search for/detect SL_SYCH, on a SL BWP signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network cannot be selected as a synchronization reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network cannot be selected as a synchronization reference. On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 to the PRIORITY 5 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network can be selected as a synchronization reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a SL BWP signaled/indicated that a base station/network can be selected as a synchronization reference.

For example, the network/base station may transmit/signal, to the UE, information related to whether the UE applies the rule. For example, the network/base station may transmit/signal, to the UE, HOP information related to SL_SYCH for which the UE does not perform a search/detection operation. Herein, for example, if the HOP value is 0, it may refer to a UE directly synchronized with the base station or the GNSS. For example, if the HOP value is 1, it may refer to a UE (e.g., indirectly synchronized UE) synchronized with SL synchronization signal(s) transmitted by a UE directly synchronized with the base station or the GNSS.

For example, only if a time synchronization difference between the GNSS and the base station exceeds a pre-configured threshold, the rule (e.g., in the case of signalling that a base station (potentially) does not exist or in the case of signalling that a base station/network need not be considered (potentially) as a synchronization source/reference) may be limitedly applied/allowed. For example, only if a frequency synchronization difference between the GNSS and the base station exceeds a pre-configured threshold, the rule (e.g., in the case of signalling that a base station (potentially) does not exist or in the case of signalling that a base station/network need not be considered (potentially) as a synchronization source/reference) may be limitedly applied/allowed. Herein, for example, the network/base station may transmit/signal, to the UE, information related to whether time synchronization between the GNSS and the base station is aligned. For example, the network/base station may transmit/signal, to the UE, information related to whether frequency synchronization between the GNSS and the base station is aligned. For example, the network/base station may transmit/signal, to the UE, information related to whether the difference in time synchronization between the GNSS and the base station is within a pre-configured threshold error range. For example, the network/base station may transmit/signal, to the UE, information related to whether the difference in frequency synchronization between the GNSS and the base station is within a pre-configured threshold error range.

For example, if the GNSS is set to a (relatively) higher priority than the base station (e.g., if sl-SyncPriority indicates/represents gnss or sl-SyncPriority is not configured), the UE may select a synchronization reference based on the left column of Table 8. Herein, for example, the network/base station may transmit/signal, to the UE, information indicating/representing that synchronization references/sources corresponding to the PRIORITY 3, the PRIORITY 4 and the PRIORITY 5 cannot be searched/detected. For example, the network/base station may transmit/signal, to the UE, information indicating/representing that synchronization references/sources corresponding to the PRIORITY 3, the PRIORITY 4, the PRIORITY 5 and the PRIORITY 6 cannot be searched/detected.

For example, if the base station is set to a (relatively) higher priority than the GNSS (e.g., if sl-SyncPriority indicates/represents gnbEnb), the UE may select a synchronization reference based on the right column of Table 8. Herein, for example, the network/base station may transmit/signal, to the UE, information indicating/representing that synchronization references/sources corresponding to the PRIORITY 0, the PRIORITY 1 and the PRIORITY 2 cannot be searched/detected. For example, the network/base station may transmit/signal, to the UE, information indicating/representing that synchronization references/sources corresponding to the PRIORITY 0, the PRIORITY 1, the PRIORITY 2 and the PRIORITY 6 cannot be searched/detected.

Herein, in case the proposed rule is applied, for example, even if the left column of Table 8 (e.g., the GNSS has a (relatively) higher priority than the base station) or the right column of Table 8 (e.g., the base station has a (relatively) higher priority than the GNSS) is configured/used for the UE, the UE may search for/detect only GNSS-related synchronization signal(s) (e.g., synchronization signal(s) corresponding to the PRIORITY 0 in the left column of Table 8) and SL synchronization signal(s) referring to time synchronization and/or frequency synchronization of the GNSS (or derived from GNSS) (e.g., SL synchronization signal(s) corresponding to the PRIORITY 1 and the PRIORITY 2 (or the PRIORITY 6) in the left column of Table 8). In other words, for example, in case the proposed rule is applied, the UE may search for/detect a synchronization source/reference without considering the PRIORITY 3, the PRIORITY 4, and the PRIORITY 5 in the left column of Table 8. For example, in case the proposed rule is applied, the UE may search for/detect a synchronization source/reference without considering the PRIORITY 3, the PRIORITY 4, the PRIORITY 5, and the PRIORITY 6 in the left column of Table 8. For example, in case the proposed rule is applied, the UE may search for/detect a synchronization source/reference without considering the PRIORITY 0, the PRIORITY 1, and the PRIORITY 2 in the right column of Table 8. For example, in case the proposed rule is applied, the UE may search for/detect a synchronization source/reference without considering the PRIORITY 0, the PRIORITY 1, the PRIORITY 2, and the PRIORITY 6 in the right column of Table 8.

For example, i) if the UE is configured that the GNSS is set to a (relatively) higher priority than the base station (e.g., if sl-SyncPriority indicates/represents gnss or sl-SyncPriority is not configured), and ii) if the UE is configured that that the base station/network cannot be selected as a synchronization reference (e.g., if sl-NbAsSync is false), the UE may select the synchronization reference based on Table 9 or Table 10.

TABLE 9 PRIORITY 0: GNSS PRIORITY 1: UE directly synchronized with GNSS PRIORITY 2: UE indirectly synchronized with GNSS PRIORITY 3: remaining UE(s) having lowest priority

TABLE 10 4> if sl-SyncPriority corresponding to the concerned frequency is set   to gnss, and sl-NbAsSync is set to false:  5> UEs of which SLSSID is 0, and inCoverage, included in the    MasterInformationBlockSidelink message received from this    UE, is set to true, or of which SLSSID is 0 and SLSS is    transmitted on slot(s) indicated by sl-SSB-TimeAllocation3,    starting with the UE with thehighest PSBCH-RSRP result    (priority group 1);  5> UEs of which SLSSID is 0 and SLSS is not transmitted on    slot(s) indicated by sl-SSB-TimeAllocation3, and inCoverage,    included in the MasterInformationBlockSidelink message    received from this UE, is set to false, starting with the UE with    the highest PSBCHS-RSRP result (priority group 2);  5> UEs of which SLSSID is 337 and inCoverage, included in the    MasterInformationBlockSidelink message received from this    UE, is set to false, starting with the UE with the highest    PSBCH-RSRP result (priority group 2);  5> Other UEs, starting with the UE with the highest PSBCH-    RSRP result (priority group 3);

For example, i) if the UE is configured that the GNSS is set to a (relatively) higher priority than the base station (e.g., if sl-SyncPriority indicates/represents gnss or sl-SyncPriority is not configured), and ii) if the UE is configured that that the base station/network can be selected as a synchronization reference (e.g., if sl-NbAsSync is true), the UE may select the synchronization reference based on Table 11 or Table 12.

TABLE 11 PRIORITY 0: GNSS PRIORITY 1: UE directly synchronized with GNSS PRIORITY 2: UE indirectly synchronized with GNSS PRIORITY 3: BS PRIORITY 4: UE directly synchronized with BS PRIORITY 5: UE indirectly synchronized with BS PRIORITY 6: remaining UE(s) having lowest priority

TABLE 12 1> if sl-SyncPriority corresponding to the concerned frequency is set   to gnss, and sl-NbAsSync is set to true:  2> UEs of which SLSSID is 0, and inCoverage, included in the    MasterInformationBlockSidelink message received from this    UE, is set to true, or of which SLSSID is 0 and SLSS is    transmitted on slot(s) indicated by sl-SSB-TimeAllocation3,    starting with the UE with the highest PSBCH-RSRP result    (priority group 1);  2> UEs of which SLSSID is 0 and SLSS is not transmitted on    slot(s) indicated by sl-SSB-TimeAllocation3, and inCoverage,    included in the MasterInformationBlockSidelink message    received from this UE, is set to false, starting with the UE with    the highestPSBCHS-RSRP result (priority group 2);  2> UEs of which SLSSID is 337 and inCoverage, included in the    MasterInformationBlockSidelink message received from this    UE, is set to false, starting with the UE with the highest    PSBCH-RSRP result (priority group 2);  2> the cell detecteted by the UE as defined in 5.8.6.3    (priority group 3);  2> UEs of which SLSSID is part of the set defined for in coverage,    and inCoverage, included in the MasterInformationBlockSide-    link message received from this UE, is set to true, starting with    the UE with the highest PSBCH-RSRP result (priority group 4);  2> UE of which SLSSID is part of the set defined for in coverage,    and inCoverage, included in the MasterInformationBlockSide-    link message received from this UE, is set to false, starting with    the UE with the highest PSBCH-RSRP result (priority group 5);  2> Other UEs, starting with the UE with the highest S-RSRP result    (priority group 6);

For example, various embodiments of the present disclosure described above may be extended/applied even when the network/base station transmits/signals information related to whether the GNSS is (potentially) considered as a synchronization source/reference to the UE. For example, information related to whether the GNSS is (potentially) considered as a synchronization source/reference may be configured for the UE for each carrier. For example, information related to whether the GNSS is (potentially) considered as a synchronization source/reference may be configured for the UE for each resource pool. For example, information related to whether the GNSS is (potentially) considered as a synchronization source/reference may be configured for the UE for each SL BWP.

For example, the UE may be configured not to search for/detect GNSS-related synchronization signal(s), on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. In the present disclosure, for convenience of description, GNSS-related synchronization signal(s) (e.g., synchronization-related signal(s) transmitted by a GNSS) may be referred to as GNS_SYN. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 0 in the left column of Table 8, on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 3 in the right column of Table 8, on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. Additionally, for example, the UE may be configured not to search for/detect SL synchronization signal(s) referring to time synchronization and/or frequency synchronization of the GNSS or SL synchronization signal(s) derived from a time and/or a frequency of the GNSS, on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. In the present disclosure, for convenience of description, the SL synchronization signal(s) referring to the time synchronization and/or the frequency synchronization of the GNSS or the SL synchronization signal(s) derived from the time and/or the frequency of the GNSS may be referred to as SL_GNSC. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 1 and/or the PRIORITY 2 in the left column of Table 8, on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 1 and/or the PRIORITY 2 and/or the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 in the right column of Table 8, on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. For example, the UE may be configured not to search for/detect synchronization signal(s) corresponding to the PRIORITY 4 and/or the PRIORITY 5 and/or the PRIORITY 6 in the right column of Table 8, on a carrier signaled/indicated that a GNSS need not be considered (potentially) as a synchronization source/reference. On the other hand, for example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 0, the PRIORITY 1, and the PRIORITY 2 in the left column of Table 8, on a carrier signaled/indicated that a GNSS needs to be considered (potentially) as a synchronization source/reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the left column of Table 8, on a carrier signaled/indicated that a GNSS needs to be considered (potentially) as a synchronization source/reference. For example, the UE may be configured to search for/detect synchronization signal(s) corresponding to the PRIORITY 3, the PRIORITY 4, and the PRIORITY 5 in the right column of Table 8, on a carrier signaled/indicated that a GNSS needs to be considered (potentially) as a synchronization source/reference. In this case, the UE may search for/detect all synchronization signals corresponding to the PRIORITY 0 to the PRIORITY 6 in the right column of Table 8, on a carrier signaled/indicated that a GNSS needs to be considered (potentially) as a synchronization source/reference. Herein, the carrier may be replaced with a SL BWP or a resource pool.

In step S1330, the UE may obtain synchronization from the synchronization reference selected in step S1320. For example, the synchronization may include time synchronization and/or frequency synchronization.

In step S1340, the UE may perform SL communication based on the obtained synchronization.

For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each service type (allowed for each carrier or for each resource pool or for each SL BWP). For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each service priority. For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each QoS parameter/requirement. For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each carrier type (e.g., a licensed carrier or an Intelligent Transportation System (ITS) dedicated carrier). For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each center frequency of a carrier. For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each resource pool of a carrier. For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each UE speed in a carrier. For example, whether the rule proposed in the present disclosure applies or not, may be configured differently or independently for the UE (from the network or the base station) for each congestion level (e.g., CBR) of a carrier.

FIG. 14 shows a method for a first device to perform synchronization, based on an embodiment of the present disclosure. The embodiment of FIG. 14 may be combined with various embodiments of the present disclosure.

Referring to FIG. 14 , in step S1410, the first device may search for/detect a synchronization source or a synchronization reference. For example, the first device may search for/detect the synchronization source or the synchronization reference, based on various methods and/or procedures proposed in the present disclosure. In step S1420, the first device may perform synchronization based on the synchronization source or the synchronization reference. For example, the first device may perform synchronization based on the synchronization source or the synchronization reference, based on various methods and/or procedures proposed in the present disclosure. For example, the first device may receive information on a priority of synchronization source(s) or synchronization reference(s) from a network or a base station. For example, the network or the base station may configure or pre-configure information on the priority of synchronization source(s) or synchronization reference(s) to the first device. For example, the first device may receive, from the network or the base station, information on whether a gNB and/or an eNB can exist for each carrier or for each resource pool or for each SL BWP. For example, the network or the base station may configure or pre-configure information on whether the gNB and/or the eNB can exist for each carrier or for each resource pool or for each SL BWP to the first device. For example, the first device may receive, from the network or the base station, information on whether the gNB and/or the eNB should be considered potentially for each carrier or for each resource pool or for each SL BWP. For example, the network or the base station may configure or pre-configure information on whether the gNB and/or the eNB should be considered potentially for each carrier or for each resource pool or for each SL BWP to the first device.

FIG. 15 shows a method for a second device to perform synchronization, based on an embodiment of the present disclosure. The embodiment of FIG. 15 may be combined with various embodiments of the present disclosure.

Referring to FIG. 15 , in step S1510, the second device may search for/detect a synchronization source or a synchronization reference. For example, the second device may search for/detect the synchronization source or the synchronization reference, based on various methods and/or procedures proposed in the present disclosure. In step S1520, the second device may perform synchronization based on the synchronization source or the synchronization reference. For example, the second device may perform synchronization based on the synchronization source or the synchronization reference, based on various methods and/or procedures proposed in the present disclosure. For example, the second device may receive, from the network or the base station, information on a priority of synchronization source(s) or synchronization reference(s). For example, the network or the base station may configure or pre-configure information on the priority of synchronization source(s) or synchronization reference(s) to the second device. For example, the second device may receive, from the network or the base station, information on whether a gNB and/or an eNB can exist for each carrier or for each resource pool or for each SL BWP. For example, the network or the base station may configure or pre-configure information on whether the gNB and/or the eNB can exist for each carrier or for each resource pool or for each SL BWP to the second device. For example, the second device may receive, from the network or the base station, information on whether the gNB and/or eNB should be considered potentially for each carrier or for each resource pool or for each SL BWP. For example, the network or the base station may configure or pre-configure information on whether the gNB and/or the eNB should be considered potentially for each carrier or for each resource pool or for each SL BWP to the second device.

FIG. 16 shows a method for a first device to perform wireless communication, based on an embodiment of the present disclosure. The embodiment of FIG. 16 may be combined with various embodiments of the present disclosure.

Referring to FIG. 16 , in step S1610, the first device may receive, from a base station (BS), first information related to sidelink (SL) synchronization priority order. For example, the first information may be set to Global Navigation Satellite Systems (GNSS)-based synchronization. For example, synchronization references related to the GNSS-based synchronization may include a GNSS, GNSS-related synchronization references, BS-related synchronization references, and other user equipments (UEs). For example, the GNSS-related synchronization references may include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS. For example, the BS-related synchronization references may include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS. For example, the GNSS may have a higher synchronization priority than the UE directly synchronized with the GNSS, and the UE directly synchronized with the GNSS may have a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS may have a higher synchronization priority than the BS, and the BS may have a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS may have a higher synchronization priority than the UE indirectly synchronized with the BS, and the UE indirectly synchronized with the BS may have a higher synchronization priority than the other UEs. In step S1620, the first device may receive, from the BS, second information representing whether or not the BS-related synchronization references can be selected as a synchronization source. In step S1630, the first device may perform synchronization with one synchronization reference among the GNSS-related synchronization references and the other UEs, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

Additionally, for example, the first device may select one synchronization reference from among the GNSS-related synchronization references and the other UEs, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source. For example, the BS-related synchronization references may not be selected as a synchronization reference, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

Additionally, for example, the first device may perform synchronization with one synchronization reference among the GNSS-related synchronization references, the BS-related synchronization references, and the other UEs, based on the second information representing that the BS-related synchronization references can be selected as the synchronization source.

For example, the first device may be a device that has not selected the GNSS as a synchronization reference.

For example, performing the synchronization with the one synchronization reference may comprise: obtaining the synchronization related to SL communication based on a signal related to synchronization transmitted by the one synchronization reference.

For example, the other UEs may be UEs which are not directly or indirectly synchronized with the GNSS and are not directly or indirectly synchronized with the BS.

For example, the first device may not detect a signal related to synchronization transmitted by the BS-related synchronization references, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

For example, the second information may be configured for each carrier, for each resource pool or for each frequency.

Additionally, for example, the first device may measure Reference Signal Received Power (RSRP) based on a signal related to synchronization transmitted by the GNSS-related synchronization references or the other UEs. For example, the RSRP measured based on a signal related to synchronization transmitted by the one synchronization reference may exceed a pre-configured threshold. For example, the one synchronization reference may have a highest synchronization priority among the GNSS-related synchronization references and the other UEs.

For example, the second information may be received from the BS based on a synchronization difference between the GNSS and the BS exceeds a pre-configured threshold. For example, the synchronization difference may include at least one of a synchronization difference related to a frequency or a synchronization difference related to a time.

The proposed method can be applied to the device(s) described below. First, the processor 102 of the first device 100 may control the transceiver 106 to receive, from a base station (BS), first information related to sidelink (SL) synchronization priority order. For example, the first information may be set to Global Navigation Satellite Systems (GNSS)-based synchronization. For example, synchronization references related to the GNSS-based synchronization may include a GNSS, GNSS-related synchronization references, BS-related synchronization references, and other user equipments (UEs). For example, the GNSS-related synchronization references may include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS. For example, the BS-related synchronization references may include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS. For example, the GNSS may have a higher synchronization priority than the UE directly synchronized with the GNSS, and the UE directly synchronized with the GNSS may have a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS may have a higher synchronization priority than the BS, and the BS may have a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS may have a higher synchronization priority than the UE indirectly synchronized with the BS, and the UE indirectly synchronized with the BS may have a higher synchronization priority than the other UEs. In addition, the processor 102 of the first device 100 may control the transceiver 106 to receive, from the BS, second information representing whether or not the BS-related synchronization references can be selected as a synchronization source. In addition, the processor 102 of the first device 100 may perform synchronization with one synchronization reference among the GNSS-related synchronization references and the other UEs, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

Based on an embodiment of the present disclosure, a first device configured to perform wireless communication may be provided. For example, the first device may comprise: one or more memories storing instructions; one or more transceivers; and one or more processors connected to the one or more memories and the one or more transceivers. For example, the one or more processors may execute the instructions to: receive, from a base station (BS), first information related to sidelink (SL) synchronization priority order, wherein the first information is set to Global Navigation Satellite Systems (GNSS)-based synchronization, wherein synchronization references related to the GNSS-based synchronization include a GNSS, GNSS-related synchronization references, BS-related synchronization references, and other user equipments (UEs), wherein the GNSS-related synchronization references include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS, wherein the BS-related synchronization references include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS, and wherein the GNSS has a higher synchronization priority than the UE directly synchronized with the GNSS, and the UE directly synchronized with the GNSS has a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS has a higher synchronization priority than the BS, and the BS has a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS has a higher synchronization priority than the UE indirectly synchronized with the BS, and the UE indirectly synchronized with the BS has a higher synchronization priority than the other UEs; receive, from the BS, second information representing whether or not the BS-related synchronization references can be selected as a synchronization source; and perform synchronization with one synchronization reference among the GNSS-related synchronization references and the other UEs, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

Based on an embodiment of the present disclosure, an apparatus configured to control a first user equipment (UE) performing wireless communication may be provided. For example, the apparatus may comprise: one or more processors; and one or more memories operably connected to the one or more processors and storing instructions. For example, the one or more processors may execute the instructions to: receive, from a base station (BS), first information related to sidelink (SL) synchronization priority order, wherein the first information is set to Global Navigation Satellite Systems (GNSS)-based synchronization, wherein synchronization references related to the GNSS-based synchronization include a GNSS, GNSS-related synchronization references, BS-related synchronization references, and other UEs, wherein the GNSS-related synchronization references include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS, wherein the BS-related synchronization references include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS, and wherein the GNSS has a higher synchronization priority than the UE directly synchronized with the GNSS, and the UE directly synchronized with the GNSS has a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS has a higher synchronization priority than the BS, and the BS has a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS has a higher synchronization priority than the UE indirectly synchronized with the BS, and the UE indirectly synchronized with the BS has a higher synchronization priority than the other UEs; receive, from the BS, second information representing whether or not the BS-related synchronization references can be selected as a synchronization source; and perform synchronization with one synchronization reference among the GNSS-related synchronization references and the other UEs, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

Based on an embodiment of the present disclosure, a non-transitory computer-readable storage medium storing instructions may be provided. For example, the instructions, when executed, may cause a first device to: receive, from a base station (BS), first information related to sidelink (SL) synchronization priority order, wherein the first information is set to Global Navigation Satellite Systems (GNSS)-based synchronization, wherein synchronization references related to the GNSS-based synchronization include a GNSS, GNSS-related synchronization references, BS-related synchronization references, and other user equipments (UEs), wherein the GNSS-related synchronization references include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS, wherein the BS-related synchronization references include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS, and wherein the GNSS has a higher synchronization priority than the UE directly synchronized with the GNSS, and the UE directly synchronized with the GNSS has a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS has a higher synchronization priority than the BS, and the BS has a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS has a higher synchronization priority than the UE indirectly synchronized with the BS, and the UE indirectly synchronized with the BS has a higher synchronization priority than the other UEs; receive, from the BS, second information representing whether or not the BS-related synchronization references can be selected as a synchronization source; and perform synchronization with one synchronization reference among the GNSS-related synchronization references and the other UEs, based on the second information representing that the BS-related synchronization references cannot be selected as the synchronization source.

FIG. 17 shows a method for a first device to perform wireless communication, based on an embodiment of the present disclosure. The embodiment of FIG. 17 may be combined with various embodiments of the present disclosure.

Referring to FIG. 17 , in step S1710, the first device may receive information related to a sidelink (SL) bandwidth part (BWP). For example, the first device may receive, from a network, information related to a sidelink (SL) bandwidth part (BWP). In step S1720, the first device may receive, from a network, SL synchronization priority order information which is set to Global Navigation Satellite Systems (GNSS)-based synchronization. In step S1730, the first device may receive, from the network, information representing whether or not base station (BS)-related synchronization references are disabled to be selected. In step S1740, the first device may detect a synchronization signal transmitted through the SL BWP by GNSS-related synchronization references or other user equipments (UEs), based on the information representing that the BS-related synchronization references are disabled to be selected. In step S1750, the first device may perform synchronization with one synchronization reference, based on the synchronization signal, among the GNSS-related synchronization references or the other UEs. For example, synchronization references related to the GNSS-based synchronization may include a GNSS, the GNSS-related synchronization references, the BS-related synchronization references, and the other UEs. For example, the GNSS-related synchronization references may include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS. For example, the BS-related synchronization references may include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS.

For example, based on the SL synchronization priority order information, the GNSS-related synchronization references may prioritize over the BS-related synchronization references.

For example, performing the synchronization with the one synchronization reference may comprise: obtaining the synchronization related to SL communication based on the synchronization signal transmitted through the SL BWP by the one synchronization reference.

Additionally, for example, the first device may select the one synchronization reference from among the GNSS-related synchronization references and the other UEs. For example, based on the information representing that the BS-related synchronization references are disabled to be selected, the BS-related synchronization references may not be selected as a synchronization reference.

For example, the first device may be a device that has not selected the GNSS as a synchronization reference

For example, based on the information representing that the BS-related synchronization references are disabled to be selected, the first device may not detect a synchronization signal transmitted by the BS-related synchronization references.

Additionally, for example, the first device may detect a synchronization signal transmitted by the GNSS-related synchronization references, the BS-related synchronization references, or the other UEs, based on the information representing that the BS-related synchronization references are enabled to be selected. Additionally, for example, the first device may perform synchronization with one synchronization reference, based on the synchronization signal, among the GNSS-related synchronization references, the BS-related synchronization references, or the other UEs.

For example, the other UEs may be UEs that are not directly or indirectly synchronized with the GNSS and are not directly or indirectly synchronized with the BS.

For example, the information representing whether or not the BS-related synchronization references are disabled to be selected may be configured for each carrier, for each resource pool or for each frequency.

Additionally, for example, the first device may measure Reference Signal Received Power (RSRP) based on the synchronization signal transmitted through the SL BWP by the GNSS-related synchronization references or the other UEs. Additionally, for example, the first device may determine one or more synchronization references related to at least one RSRP value exceeding a pre-configured threshold value, among RSRP values measured for the GNSS-related synchronization references or the other UEs. Additionally, for example, the first device may select the one synchronization reference with a highest synchronization priority among the one or more synchronization references. For example, the GNSS may have a higher synchronization priority than the UE directly synchronized with the GNSS, and the UE directly synchronized with the GNSS may have a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS may have a higher synchronization priority than the BS, and the BS may have a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS may have a higher synchronization priority than the UE indirectly synchronized with the BS, and the UE indirectly synchronized with the BS may have a higher synchronization priority than the other UEs.

The proposed method can be applied to the device(s) described below. First, the processor 102 of the first device 100 may control the transceiver 106 to receive information related to a sidelink (SL) bandwidth part (BWP). In addition, the processor 102 of the first device 100 may control the transceiver 106 to receive, from a network, SL synchronization priority order information which is set to Global Navigation Satellite Systems (GNSS)-based synchronization. In addition, the processor 102 of the first device 100 may control the transceiver 106 to receive, from the network, information representing whether or not base station (BS)-related synchronization references are disabled to be selected. In addition, the processor 102 of the first device 100 may detect a synchronization signal transmitted through the SL BWP by GNSS-related synchronization references or other user equipments (UEs), based on the information representing that the BS-related synchronization references are disabled to be selected. In addition, the processor 102 of the first device 100 may perform synchronization with one synchronization reference, based on the synchronization signal, among the GNSS-related synchronization references or the other UEs. For example, synchronization references related to the GNSS-based synchronization may include a GNSS, the GNSS-related synchronization references, the BS-related synchronization references, and the other UEs. For example, the GNSS-related synchronization references may include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS. For example, the BS-related synchronization references may include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS.

Based on an embodiment of the present disclosure, a first device configured to perform wireless communication may be provided. For example, the first device may comprise: one or more memories storing instructions; one or more transceivers; and one or more processors connected to the one or more memories and the one or more transceivers. For example, the one or more processors may execute the instructions to: receive information related to a sidelink (SL) bandwidth part (BWP); receive, from a network, SL synchronization priority order information which is set to Global Navigation Satellite Systems (GNSS)-based synchronization; receive, from the network, information representing whether or not base station (BS)-related synchronization references are disabled to be selected; detect a synchronization signal transmitted through the SL BWP by GNSS-related synchronization references or other user equipments (UEs), based on the information representing that the BS-related synchronization references are disabled to be selected; and perform synchronization with one synchronization reference, based on the synchronization signal, among the GNSS-related synchronization references or the other UEs. For example, synchronization references related to the GNSS-based synchronization may include a GNSS, the GNSS-related synchronization references, the BS-related synchronization references, and the other UEs, and the GNSS-related synchronization references may include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS, and the BS-related synchronization references may include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS.

Based on an embodiment of the present disclosure, an apparatus configured to control a first user equipment (UE) performing wireless communication may be provided. For example, the apparatus may comprise: one or more processors; and one or more memories operably connected to the one or more processors and storing instructions. For example, the one or more processors may execute the instructions to: receive information related to a sidelink (SL) bandwidth part (BWP); receive, from a network, SL synchronization priority order information which is set to Global Navigation Satellite Systems (GNSS)-based synchronization; receive, from the network, information representing whether or not base station (BS)-related synchronization references are disabled to be selected; detect a synchronization signal transmitted through the SL BWP by GNSS-related synchronization references or other UEs, based on the information representing that the BS-related synchronization references are disabled to be selected; and perform synchronization with one synchronization reference, based on the synchronization signal, among the GNSS-related synchronization references or the other UEs. For example, synchronization references related to the GNSS-based synchronization may include a GNSS, the GNSS-related synchronization references, the BS-related synchronization references, and the other UEs, and the GNSS-related synchronization references may include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS, and the BS-related synchronization references may include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS.

Based on an embodiment of the present disclosure, a non-transitory computer-readable storage medium storing instructions may be provided. For example, the instructions, when executed, may cause a first device to: receive information related to a sidelink (SL) bandwidth part (BWP); receive, from a network, SL synchronization priority order information which is set to Global Navigation Satellite Systems (GNSS)-based synchronization; receive, from the network, information representing whether or not base station (BS)-related synchronization references are disabled to be selected; detect a synchronization signal transmitted through the SL BWP by GNSS-related synchronization references or other user equipments (UEs), based on the information representing that the BS-related synchronization references are disabled to be selected; and perform synchronization with one synchronization reference, based on the synchronization signal, among the GNSS-related synchronization references or the other UEs. For example, synchronization references related to the GNSS-based synchronization may include a GNSS, the GNSS-related synchronization references, the BS-related synchronization references, and the other UEs, and the GNSS-related synchronization references may include a UE directly synchronized with the GNSS, and a UE indirectly synchronized with the GNSS, and the BS-related synchronization references may include a BS, a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS.

Various embodiments of the present disclosure may be combined with each other.

Hereinafter, device(s) to which various embodiments of the present disclosure can be applied will be described.

The various descriptions, functions, procedures, proposals, methods, and/or operational flowcharts of the present disclosure described in this document may be applied to, without being limited to, a variety of fields requiring wireless communication/connection (e.g., 5G between devices.

Hereinafter, a description will be given in more detail with reference to the drawings. In the following drawings/description, the same reference symbols may denote the same or corresponding hardware blocks, software blocks, or functional blocks unless described otherwise.

FIG. 18 shows a communication system 1, based on an embodiment of the present disclosure.

Referring to FIG. 18 , a communication system 1 to which various embodiments of the present disclosure are applied includes wireless devices, Base Stations (BSs), and a network. Herein, the wireless devices represent devices performing communication using Radio Access Technology (RAT) (e.g., 5G New RAT (NR)) or Long-Term Evolution (LTE)) and may be referred to as communication/radio/5G devices. The wireless devices may include, without being limited to, a robot 100 a, vehicles 100 b-1 and 100 b-2, an eXtended Reality (XR) device 100 c, a hand-held device 100 d, a home appliance 100 e, an Internet of Things (IoT) device 100 f, and an Artificial Intelligence (AI) device/server 400. For example, the vehicles may include a vehicle having a wireless communication function, an autonomous vehicle, and a vehicle capable of performing communication between vehicles. Herein, the vehicles may include an Unmanned Aerial Vehicle (UAV) (e.g., a drone). The XR device may include an Augmented Reality (AR)/Virtual Reality (VR)/Mixed Reality (MR) device and may be implemented in the form of a Head-Mounted Device (HMD), a Head-Up Display (HUD) mounted in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, etc. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), and a computer (e.g., a notebook). The home appliance may include a TV, a refrigerator, and a washing machine. The IoT device may include a sensor and a smartmeter. For example, the BSs and the network may be implemented as wireless devices and a specific wireless device 200 a may operate as a BS/network node with respect to other wireless devices.

Here, wireless communication technology implemented in wireless devices 100 a to 100 f of the present disclosure may include Narrowband Internet of Things for low-power communication in addition to LTE, NR, and 6G. In this case, for example, NB-IoT technology may be an example of Low Power Wide Area Network (LPWAN) technology and may be implemented as standards such as LTE Cat NB1, and/or LTE Cat NB2, and is not limited to the name described above. Additionally or alternatively, the wireless communication technology implemented in the wireless devices 100 a to 100 f of the present disclosure may perform communication based on LTE-M technology. In this case, as an example, the LTE-M technology may be an example of the LPWAN and may be called by various names including enhanced Machine Type Communication (eMTC), and the like. For example, the LTE-M technology may be implemented as at least any one of various standards such as 1) LTE CAT 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-Bandwidth Limited (non-BL), 5) LTE-MTC, 6) LTE Machine Type Communication, and/or 7) LTE M, and is not limited to the name described above. Additionally or alternatively, the wireless communication technology implemented in the wireless devices 100 a to 100 f of the present disclosure may include at least one of Bluetooth, Low Power Wide Area Network (LPWAN), and ZigBee considering the low-power communication, and is not limited to the name described above. As an example, the ZigBee technology may generate personal area networks (PAN) related to small/low-power digital communication based on various standards including IEEE 802.15.4, and the like, and may be called by various names.

The wireless devices 100 a to 100 f may be connected to the network 300 via the BSs 200. An AI technology may be applied to the wireless devices 100 a to 100 f and the wireless devices 100 a to 100 f may be connected to the AI server 400 via the network 300. The network 300 may be configured using a 3G network, a 4G (e.g., LTE) network, or a 5G (e.g., NR) network. Although the wireless devices 100 a to 100 f may communicate with each other through the BSs 200/network 300, the wireless devices 100 a to 100 f may perform direct communication (e.g., sidelink communication) with each other without passing through the BSs/network. For example, the vehicles 100 b-1 and 100 b-2 may perform direct communication (e.g. Vehicle-to-Vehicle (V2V)/Vehicle-to-everything (V2X) communication). The IoT device (e.g., a sensor) may perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100 a to 100 f.

Wireless communication/connections 150 a, 150 b, or 150 c may be established between the wireless devices 100 a to 100 f/BS 200, or BS 200/BS 200. Herein, the wireless communication/connections may be established through various RATs (e.g., 5G NR) such as uplink/downlink communication 150 a, sidelink communication 150 b (or, D2D communication), or inter BS communication (e.g., relay, Integrated Access Backhaul (IAB)). The wireless devices and the BSs/the wireless devices may transmit/receive radio signals to/from each other through the wireless communication/connections 150 a and 150 b. For example, the wireless communication/connections 150 a and 150 b may transmit/receive signals through various physical channels. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, and resource mapping/demapping), and resource allocating processes, for transmitting/receiving radio signals, may be performed based on the various proposals of the present disclosure.

FIG. 19 shows wireless devices, based on an embodiment of the present disclosure.

Referring to FIG. 19 , a first wireless device 100 and a second wireless device 200 may transmit radio signals through a variety of RATs (e.g., LTE and NR). Herein, {the first wireless device 100 and the second wireless device 200} may correspond to {the wireless device 100 x and the BS 200} and/or {the wireless device 100 x and the wireless device 100 x} of FIG. 18 .

The first wireless device 100 may include one or more processors 102 and one or more memories 104 and additionally further include one or more transceivers 106 and/or one or more antennas 108. The processor(s) 102 may control the memory(s) 104 and/or the transceiver(s) 106 and may be configured to implement the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. For example, the processor(s) 102 may process information within the memory(s) 104 to generate first information/signals and then transmit radio signals including the first information/signals through the transceiver(s) 106. The processor(s) 102 may receive radio signals including second information/signals through the transceiver 106 and then store information obtained by processing the second information/signals in the memory(s) 104. The memory(s) 104 may be connected to the processor(s) 102 and may store a variety of information related to operations of the processor(s) 102. For example, the memory(s) 104 may store software code including commands for performing a part or the entirety of processes controlled by the processor(s) 102 or for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. Herein, the processor(s) 102 and the memory(s) 104 may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver(s) 106 may be connected to the processor(s) 102 and transmit and/or receive radio signals through one or more antennas 108. Each of the transceiver(s) 106 may include a transmitter and/or a receiver. The transceiver(s) 106 may be interchangeably used with Radio Frequency (RF) unit(s). In the present disclosure, the wireless device may represent a communication modem/circuit/chip.

The second wireless device 200 may include one or more processors 202 and one or more memories 204 and additionally further include one or more transceivers 206 and/or one or more antennas 208. The processor(s) 202 may control the memory(s) 204 and/or the transceiver(s) 206 and may be configured to implement the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. For example, the processor(s) 202 may process information within the memory(s) 204 to generate third information/signals and then transmit radio signals including the third information/signals through the transceiver(s) 206. The processor(s) 202 may receive radio signals including fourth information/signals through the transceiver(s) 106 and then store information obtained by processing the fourth information/signals in the memory(s) 204. The memory(s) 204 may be connected to the processor(s) 202 and may store a variety of information related to operations of the processor(s) 202. For example, the memory(s) 204 may store software code including commands for performing a part or the entirety of processes controlled by the processor(s) 202 or for performing the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. Herein, the processor(s) 202 and the memory(s) 204 may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver(s) 206 may be connected to the processor(s) 202 and transmit and/or receive radio signals through one or more antennas 208. Each of the transceiver(s) 206 may include a transmitter and/or a receiver. The transceiver(s) 206 may be interchangeably used with RF unit(s). In the present disclosure, the wireless device may represent a communication modem/circuit/chip.

Hereinafter, hardware elements of the wireless devices 100 and 200 will be described more specifically. One or more protocol layers may be implemented by, without being limited to, one or more processors 102 and 202. For example, the one or more processors 102 and 202 may implement one or more layers (e.g., functional layers such as PHY, MAC, RLC, PDCP, RRC, and SDAP). The one or more processors 102 and 202 may generate one or more Protocol Data Units (PDUs) and/or one or more Service Data Unit (SDUs) according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. The one or more processors 102 and 202 may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document. The one or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document and provide the generated signals to the one or more transceivers 106 and 206. The one or more processors 102 and 202 may receive the signals (e.g., baseband signals) from the one or more transceivers 106 and 206 and acquire the PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document.

The one or more processors 102 and 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The one or more processors 102 and 202 may be implemented by hardware, firmware, software, or a combination thereof. As an example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in the one or more processors 102 and 202. The descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document may be implemented using firmware or software and the firmware or software may be configured to include the modules, procedures, or functions. Firmware or software configured to perform the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document may be included in the one or more processors 102 and 202 or stored in the one or more memories 104 and 204 so as to be driven by the one or more processors 102 and 202. The descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document may be implemented using firmware or software in the form of code, commands, and/or a set of commands.

The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, code, instructions, and/or commands. The one or more memories 104 and 204 may be configured by Read-Only Memories (ROMs), Random Access Memories (RAMs), Electrically Erasable Programmable Read-Only Memories (EPROMs), flash memories, hard drives, registers, cash memories, computer-readable storage media, and/or combinations thereof. The one or more memories 104 and 204 may be located at the interior and/or exterior of the one or more processors 102 and 202. The one or more memories 104 and 204 may be connected to the one or more processors 102 and 202 through various technologies such as wired or wireless connection.

The one or more transceivers 106 and 206 may transmit user data, control information, and/or radio signals/channels, mentioned in the methods and/or operational flowcharts of this document, to one or more other devices. The one or more transceivers 106 and 206 may receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document, from one or more other devices. For example, the one or more transceivers 106 and 206 may be connected to the one or more processors 102 and 202 and transmit and receive radio signals. For example, the one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may transmit user data, control information, or radio signals to one or more other devices. The one or more processors 102 and 202 may perform control so that the one or more transceivers 106 and 206 may receive user data, control information, or radio signals from one or more other devices. The one or more transceivers 106 and 206 may be connected to the one or more antennas 108 and 208 and the one or more transceivers 106 and 206 may be configured to transmit and receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document, through the one or more antennas 108 and 208. In this document, the one or more antennas may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports). The one or more transceivers 106 and 206 may convert received radio signals/channels etc. from RF band signals into baseband signals in order to process received user data, control information, radio signals/channels, etc. using the one or more processors 102 and 202. The one or more transceivers 106 and 206 may convert the user data, control information, radio signals/channels, etc. processed using the one or more processors 102 and 202 from the base band signals into the RF band signals. To this end, the one or more transceivers 106 and 206 may include (analog) oscillators and/or filters.

FIG. 20 shows a signal process circuit for a transmission signal, based on an embodiment of the present disclosure.

Referring to FIG. 20 , a signal processing circuit 1000 may include scramblers 1010, modulators 1020, a layer mapper 1030, a precoder 1040, resource mappers 1050, and signal generators 1060. An operation/function of FIG. 20 may be performed, without being limited to, the processors 102 and 202 and/or the transceivers 106 and 206 of FIG. 19 . Hardware elements of FIG. 20 may be implemented by the processors 102 and 202 and/or the transceivers 106 and 206 of FIG. 19 . For example, blocks 1010 to 1060 may be implemented by the processors 102 and 202 of FIG. 19 . Alternatively, the blocks 1010 to 1050 may be implemented by the processors 102 and 202 of FIG. 19 and the block 1060 may be implemented by the transceivers 106 and 206 of FIG. 19 .

Codewords may be converted into radio signals via the signal processing circuit 1000 of FIG. 20 . Herein, the codewords are encoded bit sequences of information blocks. The information blocks may include transport blocks (e.g., a UL-SCH transport block, a DL-SCH transport block). The radio signals may be transmitted through various physical channels (e.g., a PUSCH and a PDSCH).

Specifically, the codewords may be converted into scrambled bit sequences by the scramblers 1010. Scramble sequences used for scrambling may be generated based on an initialization value, and the initialization value may include ID information of a wireless device. The scrambled bit sequences may be modulated to modulation symbol sequences by the modulators 1020. A modulation scheme may include pi/2-Binary Phase Shift Keying (pi/2-BPSK), m-Phase Shift Keying (m-PSK), and m-Quadrature Amplitude Modulation (m-QAM). Complex modulation symbol sequences may be mapped to one or more transport layers by the layer mapper 1030. Modulation symbols of each transport layer may be mapped (precoded) to corresponding antenna port(s) by the precoder 1040. Outputs z of the precoder 1040 may be obtained by multiplying outputs y of the layer mapper 1030 by an N*M precoding matrix W. Herein, N is the number of antenna ports and M is the number of transport layers. The precoder 1040 may perform precoding after performing transform precoding (e.g., DFT) for complex modulation symbols. Alternatively, the precoder 1040 may perform precoding without performing transform precoding.

The resource mappers 1050 may map modulation symbols of each antenna port to time-frequency resources. The time-frequency resources may include a plurality of symbols (e.g., a CP-OFDMA symbols and DFT-s-OFDMA symbols) in the time domain and a plurality of subcarriers in the frequency domain. The signal generators 1060 may generate radio signals from the mapped modulation symbols and the generated radio signals may be transmitted to other devices through each antenna. For this purpose, the signal generators 1060 may include Inverse Fast Fourier Transform (IFFT) modules, Cyclic Prefix (CP) inserters, Digital-to-Analog Converters (DACs), and frequency up-converters.

Signal processing procedures for a signal received in the wireless device may be configured in a reverse manner of the signal processing procedures 1010 to 1060 of FIG. 20 . For example, the wireless devices (e.g., 100 and 200 of FIG. 19 ) may receive radio signals from the exterior through the antenna ports/transceivers. The received radio signals may be converted into baseband signals through signal restorers. To this end, the signal restorers may include frequency downlink converters, Analog-to-Digital Converters (ADCs), CP remover, and Fast Fourier Transform (FFT) modules. Next, the baseband signals may be restored to codewords through a resource demapping procedure, a postcoding procedure, a demodulation processor, and a descrambling procedure. The codewords may be restored to original information blocks through decoding. Therefore, a signal processing circuit (not illustrated) for a reception signal may include signal restorers, resource demappers, a postcoder, demodulators, descramblers, and decoders.

FIG. 21 shows another example of a wireless device, based on an embodiment of the present disclosure. The wireless device may be implemented in various forms according to a use-case/service (refer to FIG. 18 ).

Referring to FIG. 21 , wireless devices 100 and 200 may correspond to the wireless devices 100 and 200 of FIG. 19 and may be configured by various elements, components, units/portions, and/or modules. For example, each of the wireless devices 100 and 200 may include a communication unit 110, a control unit 120, a memory unit 130, and additional components 140. The communication unit may include a communication circuit 112 and transceiver(s) 114. For example, the communication circuit 112 may include the one or more processors 102 and 202 and/or the one or more memories 104 and 204 of FIG. 19 . For example, the transceiver(s) 114 may include the one or more transceivers 106 and 206 and/or the one or more antennas 108 and 208 of FIG. 19 . The control unit 120 is electrically connected to the communication unit 110, the memory 130, and the additional components 140 and controls overall operation of the wireless devices. For example, the control unit 120 may control an electric/mechanical operation of the wireless device based on programs/code/commands/information stored in the memory unit 130. The control unit 120 may transmit the information stored in the memory unit 130 to the exterior (e.g., other communication devices) via the communication unit 110 through a wireless/wired interface or store, in the memory unit 130, information received through the wireless/wired interface from the exterior (e.g., other communication devices) via the communication unit 110.

The additional components 140 may be variously configured according to types of wireless devices. For example, the additional components 140 may include at least one of a power unit/battery, input/output (I/O) unit, a driving unit, and a computing unit. The wireless device may be implemented in the form of, without being limited to, the robot (100 a of FIG. 18 ), the vehicles (100 b-1 and 100 b-2 of FIG. 18 ), the XR device (100 c of FIG. 18 ), the hand-held device (100 d of FIG. 18 ), the home appliance (100 e of FIG. 18 ), the IoT device (100 f of FIG. 18 ), a digital broadcast terminal, a hologram device, a public safety device, an MTC device, a medicine device, a fintech device (or a finance device), a security device, a climate/environment device, the AI server/device (400 of FIG. 18 ), the BSs (200 of FIG. 18 ), a network node, etc. The wireless device may be used in a mobile or fixed place according to a use-example/service.

In FIG. 21 , the entirety of the various elements, components, units/portions, and/or modules in the wireless devices 100 and 200 may be connected to each other through a wired interface or at least a part thereof may be wirelessly connected through the communication unit 110. For example, in each of the wireless devices 100 and 200, the control unit 120 and the communication unit 110 may be connected by wire and the control unit 120 and first units (e.g., 130 and 140) may be wirelessly connected through the communication unit 110. Each element, component, unit/portion, and/or module within the wireless devices 100 and 200 may further include one or more elements. For example, the control unit 120 may be configured by a set of one or more processors. As an example, the control unit 120 may be configured by a set of a communication control processor, an application processor, an Electronic Control Unit (ECU), a graphical processing unit, and a memory control processor. As another example, the memory 130 may be configured by a Random Access Memory (RAM), a Dynamic RAM (DRAM), a Read Only Memory (ROM)), a flash memory, a volatile memory, a non-volatile memory, and/or a combination thereof.

Hereinafter, an example of implementing FIG. 21 will be described in detail with reference to the drawings.

FIG. 22 shows a hand-held device, based on an embodiment of the present disclosure. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), or a portable computer (e.g., a notebook). The hand-held device may be referred to as a mobile station (MS), a user terminal (UT), a Mobile Subscriber Station (MSS), a Subscriber Station (SS), an Advanced Mobile Station (AMS), or a Wireless Terminal (WT).

Referring to FIG. 22 , a hand-held device 100 may include an antenna unit 108, a communication unit 110, a control unit 120, a memory unit 130, a power supply unit 140 a, an interface unit 140 b, and an I/O unit 140 c. The antenna unit 108 may be configured as a part of the communication unit 110. Blocks 110 to 130/140 a to 140 c correspond to the blocks 110 to 130/140 of FIG. 21 , respectively.

The communication unit 110 may transmit and receive signals (e.g., data and control signals) to and from other wireless devices or BSs. The control unit 120 may perform various operations by controlling constituent elements of the hand-held device 100. The control unit 120 may include an Application Processor (AP). The memory unit 130 may store data/parameters/programs/code/commands needed to drive the hand-held device 100. The memory unit 130 may store input/output data/information. The power supply unit 140 a may supply power to the hand-held device 100 and include a wired/wireless charging circuit, a battery, etc. The interface unit 140 b may support connection of the hand-held device 100 to other external devices. The interface unit 140 b may include various ports (e.g., an audio I/O port and a video I/O port) for connection with external devices. The I/O unit 140 c may input or output video information/signals, audio information/signals, data, and/or information input by a user. The I/O unit 140 c may include a camera, a microphone, a user input unit, a display unit 140 d, a speaker, and/or a haptic module.

As an example, in the case of data communication, the I/O unit 140 c may acquire information/signals (e.g., touch, text, voice, images, or video) input by a user and the acquired information/signals may be stored in the memory unit 130. The communication unit 110 may convert the information/signals stored in the memory into radio signals and transmit the converted radio signals to other wireless devices directly or to a BS. The communication unit 110 may receive radio signals from other wireless devices or the BS and then restore the received radio signals into original information/signals. The restored information/signals may be stored in the memory unit 130 and may be output as various types (e.g., text, voice, images, video, or haptic) through the I/O unit 140 c.

FIG. 23 shows a vehicle or an autonomous vehicle, based on an embodiment of the present disclosure. The vehicle or autonomous vehicle may be implemented by a mobile robot, a car, a train, a manned/unmanned Aerial Vehicle (AV), a ship, etc.

Referring to FIG. 23 , a vehicle or autonomous vehicle 100 may include an antenna unit 108, a communication unit 110, a control unit 120, a driving unit 140 a, a power supply unit 140 b, a sensor unit 140 c, and an autonomous driving unit 140 d. The antenna unit 108 may be configured as a part of the communication unit 110. The blocks 110/130/140 a to 140 d correspond to the blocks 110/130/140 of FIG. 21 , respectively.

The communication unit 110 may transmit and receive signals (e.g., data and control signals) to and from external devices such as other vehicles, BSs (e.g., gNBs and road side units), and servers. The control unit 120 may perform various operations by controlling elements of the vehicle or the autonomous vehicle 100. The control unit 120 may include an Electronic Control Unit (ECU). The driving unit 140 a may cause the vehicle or the autonomous vehicle 100 to drive on a road. The driving unit 140 a may include an engine, a motor, a powertrain, a wheel, a brake, a steering device, etc. The power supply unit 140 b may supply power to the vehicle or the autonomous vehicle 100 and include a wired/wireless charging circuit, a battery, etc. The sensor unit 140 c may acquire a vehicle state, ambient environment information, user information, etc. The sensor unit 140 c may include an Inertial Measurement Unit (IMU) sensor, a collision sensor, a wheel sensor, a speed sensor, a slope sensor, a weight sensor, a heading sensor, a position module, a vehicle forward/backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illumination sensor, a pedal position sensor, etc. The autonomous driving unit 140 d may implement technology for maintaining a lane on which a vehicle is driving, technology for automatically adjusting speed, such as adaptive cruise control, technology for autonomously driving along a determined path, technology for driving by automatically setting a path if a destination is set, and the like.

For example, the communication unit 110 may receive map data, traffic information data, etc. from an external server. The autonomous driving unit 140 d may generate an autonomous driving path and a driving plan from the obtained data. The control unit 120 may control the driving unit 140 a such that the vehicle or the autonomous vehicle 100 may move along the autonomous driving path according to the driving plan (e.g., speed/direction control). In the middle of autonomous driving, the communication unit 110 may aperiodically/periodically acquire recent traffic information data from the external server and acquire surrounding traffic information data from neighboring vehicles. In the middle of autonomous driving, the sensor unit 140 c may obtain a vehicle state and/or surrounding environment information. The autonomous driving unit 140 d may update the autonomous driving path and the driving plan based on the newly obtained data/information. The communication unit 110 may transfer information about a vehicle position, the autonomous driving path, and/or the driving plan to the external server. The external server may predict traffic information data using AI technology, etc., based on the information collected from vehicles or autonomous vehicles and provide the predicted traffic information data to the vehicles or the autonomous vehicles.

Claims in the present description can be combined in a various way. For instance, technical features in method claims of the present description can be combined to be implemented or performed in an apparatus, and technical features in apparatus claims can be combined to be implemented or performed in a method. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in an apparatus. Further, technical features in method claim(s) and apparatus claim(s) can be combined to be implemented or performed in a method. 

What is claimed is:
 1. A method for performing, by a first device, wireless communication, the method comprising: obtaining first information related to sidelink (SL) synchronization priority order, wherein the first information is set to Global Navigation Satellite Systems (GNSS)-based synchronization, wherein synchronization references include a user equipment (UE) directly synchronized with a GNSS, a UE indirectly synchronized with the GNSS, a base station (BS), a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS, and wherein the UE directly synchronized with the GNSS has a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS has a higher synchronization priority than the BS, and the BS has a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS has a higher synchronization priority than the UE indirectly synchronized with the BS; obtaining second information representing whether or not the BS can be selected as a synchronization reference; and performing synchronization with one synchronization reference among the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS, based on the second information representing that the BS cannot be selected as the synchronization reference.
 2. The method of claim 1, further comprising: selecting one synchronization reference from among the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS, based on the second information representing that the BS cannot be selected as the synchronization reference, wherein the BS, the UE directly synchronized with the BS and the UE indirectly synchronized with the BS are not selected as the synchronization reference, based on the second information representing that the BS cannot be selected as the synchronization reference.
 3. The method of claim 1, further comprising: performing synchronization with one synchronization reference among the UE directly synchronized with the GNSS, the UE indirectly synchronized with the GNSS, the BS, the UE directly synchronized with the BS and the UE indirectly synchronized with the BS, based on the second information representing that the BS can be selected as the synchronization reference.
 4. The method of claim 1, wherein the first device is a device that has not selected the GNSS as the synchronization reference.
 5. The method of claim 1, wherein performing the synchronization with the one synchronization reference comprises: obtaining the synchronization related to SL communication based on a signal related to synchronization transmitted by the one synchronization reference.
 6. The method of claim 1, wherein the first device does not detect a signal related to synchronization transmitted by the BS, the UE directly synchronized with the BS and the UE indirectly synchronized with the BS, based on the second information representing that the BS cannot be selected as the synchronization reference.
 7. The method of claim 1, wherein the second information is configured for each carrier, for each resource pool or for each frequency.
 8. The method of claim 1, further comprising: measuring Reference Signal Received Power (RSRP) based on a signal related to synchronization transmitted by the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS.
 9. The method of claim 8, wherein the RSRP measured based on a signal related to synchronization transmitted by the one synchronization reference exceeds a pre-configured threshold.
 10. The method of claim 9, wherein the one synchronization reference has a highest synchronization priority among the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS.
 11. The method of claim 1, wherein the second information is received from the BS based on a synchronization difference between the GNSS and the BS exceeding a pre-configured threshold.
 12. The method of claim 11, wherein the synchronization difference includes at least one of a synchronization difference related to a frequency or a synchronization difference related to a time.
 13. The method of claim 1, wherein the first information and the second information are pre-configured for the first device.
 14. A first device configured to perform wireless communication, the first device comprising: one or more transceivers; and one or more processors; one or more computer memories operably connectable to the one or more processors and storing instructions that, based on being executed, cause the one or more processors to perform operations comprising: obtaining first information related to sidelink (SL) synchronization priority order, wherein the first information is set to Global Navigation Satellite Systems (GNSS)-based synchronization, wherein synchronization references include a user equipment (UE) directly synchronized with a GNSS, a UE indirectly synchronized with the GNSS, a base station (BS), a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS, and wherein the UE directly synchronized with the GNSS has a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS has a higher synchronization priority than the BS, and the BS has a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS has a higher synchronization priority than the UE indirectly synchronized with the BS; obtaining second information representing whether or not the BS can be selected as a synchronization reference; and performing synchronization with one synchronization reference among the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS, based on the second information representing that the BS cannot be selected as the synchronization reference.
 15. The first device of claim 14, wherein the operations further comprise: selecting one synchronization reference from among the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS, based on the second information representing that the BS cannot be selected as the synchronization reference, wherein the BS, the UE directly synchronized with the BS and the UE indirectly synchronized with the BS are not selected as the synchronization reference, based on the second information representing that the BS cannot be selected as the synchronization reference.
 16. The first device of claim 14, wherein the operations further comprise: performing synchronization with one synchronization reference among the UE directly synchronized with the GNSS, the UE indirectly synchronized with the GNSS, the BS, the UE directly synchronized with the BS and the UE indirectly synchronized with the BS, based on the second information representing that the BS can be selected as the synchronization reference.
 17. The first device of claim 14, wherein the first device is a device that has not selected the GNSS as the synchronization reference.
 18. A processing device configured to control a first device performing wireless communication, the processing device comprising: one or more processors; and one or more memories operably connected to the one or more processors and storing instructions that, based on being executed, cause the one or more processors to perform operations comprising: obtaining first information related to sidelink (SL) synchronization priority order, wherein the first information is set to Global Navigation Satellite Systems (GNSS)-based synchronization, wherein synchronization references include a user equipment (UE) directly synchronized with a GNSS, a UE indirectly synchronized with the GNSS, a base station (BS), a UE directly synchronized with the BS, and a UE indirectly synchronized with the BS, and wherein the UE directly synchronized with the GNSS has a higher synchronization priority than the UE indirectly synchronized with the GNSS, and the UE indirectly synchronized with the GNSS has a higher synchronization priority than the BS, and the BS has a higher synchronization priority than the UE directly synchronized with the BS, and the UE directly synchronized with the BS has a higher synchronization priority than the UE indirectly synchronized with the BS; obtaining second information representing whether or not the BS can be selected as a synchronization reference; and performing synchronization with one synchronization reference among the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS, based on the second information representing that the BS cannot be selected as the synchronization reference.
 19. The processing device of claim 18, wherein the operations further comprise: selecting one synchronization reference from among the UE directly synchronized with the GNSS and the UE indirectly synchronized with the GNSS, based on the second information representing that the BS cannot be selected as the synchronization reference, wherein the BS, the UE directly synchronized with the BS and the UE indirectly synchronized with the BS are not selected as the synchronization reference, based on the second information representing that the BS cannot be selected as the synchronization reference.
 20. The processing device of claim 18, wherein the operations further comprise: performing synchronization with one synchronization reference among the UE directly synchronized with the GNSS, the UE indirectly synchronized with the GNSS, the BS, the UE directly synchronized with the BS and the UE indirectly synchronized with the BS, based on the second information representing that the BS can be selected as the synchronization reference. 